This is an example to show how we can update Thumbnailer and refresh its contents if changes are made in the current Path. The Thumbnailer control will refresh its contents when files are created, renamed or removed from the current Path, as an user's action or the result of a drag and drop operation.





Create the main form (Form1) and place the following components on it:
- A Thumbnailer control called "Thumbnailer"




Copy and paste to the Form the following code:


####################### CODE START ############################

Option Explicit

Private Sub Form_Load()
    
    ' Take control of message processing by installing our message
    ' handling routine into the chain of message routines for Form1
    StartWatch hWnd

End Sub


Private Sub Form_Unload(Cancel As Integer)

    ' Must return control to the system
    StopWatch hWnd

End Sub


' Use this proc to update the control in case it needs to be refreshed.
' We set this proc PUBLIC so it can be called from WindowProc in the
' mShellNotify module.
Public Sub UpdateControl(ByVal iEventID As Long, ByVal sInfoA As String, ByVal sInfoB As String)
    
  On Error Resume Next
    
  Dim sPathA As String
  Dim sPathB As String
  Dim sNameA As String
  Dim sNameB As String
    
    DoEvents
    
    ' Notification event
    Select Case iEventID
            
        ' CREATE
        '   sInfoA returns the Path(s) of the changed item(s)
        '   sInfoB is not used
        Case SHCNE_CREATE
            
			' This line is used only for information
            Debug.Print "CREATE ", sInfoA
            
            ' Get the Path of the item
            sPathA = GetFilePath(sInfoA)
            ' Get the Name of the item
            sNameA = GetFileName(sInfoA)
            ' If the Path is the current one we view in Thumbnailer
            If UCase$(sPathA) = UCase$(Thumbnailer.Path) Then
                ' Add the item into the control
                Thumbnailer.AddItem sPathA, sNameA
                ' Manually refresh contents
                Thumbnailer.DrawItems
            End If
            
        ' DELETE
        '   sInfoA returns the Path(s) of the changed item(s)
        '   sInfoB is not used
        Case SHCNE_DELETE
            
			' This line is used only for information
            Debug.Print "DELETE ", sInfoA
            
            ' Get the Path of the item
            sPathA = GetFilePath(sInfoA)
            ' Get the Name of the item
            sNameA = GetFileName(sInfoA)
            ' If the Path is the one we view in Thumbnailer
            If UCase$(sPathA) = UCase$(Thumbnailer.Path) Then
                ' Delete the item from the control
                Thumbnailer.DeleteItems sPathA & sNameA & vbNullChar & vbNullChar
                ' Manually refresh contents
                Thumbnailer.DrawItems
            End If
            
        ' RENAME
        '   sInfoA returns the previous name of the changed item
        '   sInfoB returns the new name of the changed item
        Case SHCNE_RENAMEITEM
            ' In an item is moved to another folder in the same drive,
            ' the system does not generate SHCNE_DELETE or SHCNE_CREATE
            ' messages. Instead, it generates a SHCNE_RENAMEITEM
            ' message, as it just renames the item.
            ' This is what also happens if an item is recovered from
            ' the Recycle-Bin.
            
            ' the sInfoB member contains the new name
            
			' This line is used only for information
            Debug.Print "RENAME ", sInfoA, sInfoB
            
            ' Get the previous Path of the item
            sPathA = GetFilePath(sInfoA)
            ' Get the new Path of the item
            sPathB = GetFilePath(sInfoB)
            ' If the Paths are equal, then we have a true RENAME case
            If UCase$(sPathA) = UCase$(sPathB) Then
                ' If the Paths are also equal with the one we view
                ' in Thumbnailer then we can just call RenameItem
                If UCase$(sPathA) = UCase$(Thumbnailer.Path) Then
                    ' Get the previous Name of the item
                    sNameA = GetFileName(sInfoA)
                    ' Get the new Name of the item
                    sNameB = GetFileName(sInfoB)
                    ' Rename the Thumbnailer's item
                    Thumbnailer.RenameItem sNameA, sNameB
                    ' Manually refresh contents
                    Thumbnailer.DrawItems
                End If
                ' If the Paths are not equal, then we have a MOVE case
                Else
                ' If sPathA is the current control's Path, then we have
                ' a Move operation FROM the current path to outside
                If UCase$(sPathA) = UCase$(Thumbnailer.Path) Then
                    ' Get the Name of the item is MOVED FROM path
                    sNameA = GetFileName(sInfoA)
                    ' Delete the moved item from the control
                    Thumbnailer.DeleteItems sPathA & sNameA & vbNullChar & vbNullChar
                    ' Manually refresh contents
                    Thumbnailer.DrawItems
                    ' If sPathB is the current control's Path, then we have
                    ' a Move operation from outside TO the current path
                    ElseIf UCase$(sPathB) = UCase$(Thumbnailer.Path) Then
                    ' Get the Name of the item is MOVED TO path
                    sNameB = GetFileName(sInfoB)
                    ' Add the item into the control
                    Thumbnailer.AddItem sPathB, sNameB
                    ' Manually refresh contents
                    Thumbnailer.DrawItems
                End If
            End If
        
        ' ATTRIBUTES CHANGE
        '   sInfoA returns the Path(s) of the changed item(s)
        '   sInfoB is not used
        Case SHCNE_ATTRIBUTES
            
			' This line is used only for information
            Debug.Print "ATTRIBUTES ", sInfoA
            
            ' We have to update the control if we have set the control
            ' to show Thumbnails for files with specific attributes
            ' and sInfoA concerns any item in the current Path.
            
            ' NOT IMPLEMENTED IN THIS EXAMPLE
    End Select
    
End Sub

######################## CODE END #############################




Create a BAS module (mShellNotify.bas).
Copy and paste to the module the following code:


####################### CODE START ############################

Option Explicit


Private iOldProc As Long    ' Original proc handle
Private iSHNotify As Long   ' Shell change notification handle for the desktop folder
Private iDesktopPidl As Long ' Desktop's pidl

Private Const SEPARATOR = "\"
Private Const GWL_WNDPROC = (-4)
Private Const WM_SHNOTIFY = &H401
Private Const MAX_PATH = 260


Private Enum SHGFI_flags
    SHGFI_PIDL = &H8            ' pszPath is pidl, rtns BOOL
    SHGFI_DISPLAYNAME = &H200   ' isf.szDisplayName is filled, rtns BOOL
End Enum

' Shell notification event IDs
Public Enum SHCN_EventIDs
    SHCNE_RENAMEITEM = &H1          ' (D) A nonfolder item has been renamed.
    SHCNE_CREATE = &H2              ' (D) A nonfolder item has been created.
    SHCNE_DELETE = &H4              ' (D) A nonfolder item has been deleted.
    SHCNE_ATTRIBUTES = &H800        ' (D) The attributes of an item or folder have changed.
    SHCNE_ALLEVENTSD = &H807        ' &H1 Or &H2 Or &H4 Or &H800
    SHCNE_INTERRUPT = &H80000000    ' The specified event occurred as a result of a system interrupt.
                                    ' It is stripped out before the clients of SHCNNotify_ see it.
End Enum

' Notification flags
Private Enum SHCN_ItemFlags
    SHCNF_IDLIST = &H0
    SHCNF_TYPE = &HFF
End Enum


Private Type SHFILEINFO
    hIcon As Long
    iIcon As Long
    dwAttributes As Long
    szDisplayName As String * MAX_PATH
    szTypeName As String * 80
End Type

Private Type PIDLSTRUCT
    pidl As Long    ' 0 for Desktop
    bWatchSubFolders As Long
End Type

' Notification returned info
Private Type SHNOTIFYSTRUCT
    dwItem1 As Long
    dwItem2 As Long
End Type


Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" _
                        (ByVal hWnd As Long, _
                         ByVal nIndex As Long) As Long
                         
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
                        (ByVal hWnd As Long, _
                         ByVal nIndex As Long, _
                         ByVal dwNewLong As Long) As Long

Private Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" _
                        (ByVal lpPrevWndFunc As Long, _
                         ByVal hWnd As Long, _
                         ByVal uMsg As Long, _
                         ByVal wParam As Long, _
                         ByVal lParam As Long) As Long
                         
Private Declare Function DefWindowProc Lib "user32" Alias "DefWindowProcA" _
                        (ByVal hWnd As Long, _
                         ByVal wMsg As Long, _
                         ByVal wParam As Long, _
                         ByVal lParam As Long) As Long

Private Declare Sub MoveMemory Lib "kernel32" Alias "RtlMoveMemory" _
                        (pDest As Any, _
                         pSource As Any, _
                         ByVal dwLength As Long)

Private Declare Function SHChangeNotifyRegister Lib "shell32" Alias "#2" _
                        (ByVal hWnd As Long, _
                         ByVal uFlags As SHCN_ItemFlags, _
                         ByVal dwEventID As SHCN_EventIDs, _
                         ByVal uMsg As Long, _
                         ByVal cItems As Long, _
                         lpps As PIDLSTRUCT) As Long

Private Declare Function SHChangeNotifyDeregister Lib "shell32" Alias "#4" _
                        (ByVal hNotify As Long) As Boolean

' Retrieves the location of a special (system) folder.
Private Declare Function SHGetSpecialFolderLocation Lib "shell32.dll" _
                        (ByVal hwndOwner As Long, _
                         ByVal nFolder As Long, _
                         pidl As Long) As Long

' Converts an item identifier list to a file system path.
Private Declare Function SHGetPathFromIDList Lib "shell32.dll" Alias "SHGetPathFromIDListA" _
                        (ByVal pidl As Long, _
                         ByVal pszPath As String) As Long

' Retrieves information about an object in the file system.
Private Declare Function SHGetFileInfo Lib "shell32" Alias "SHGetFileInfoA" _
                        (ByVal pszPath As Any, _
                         ByVal dwFileAttributes As Long, _
                         psfib As SHFILEINFO, _
                         ByVal cbFileInfo As Long, _
                         ByVal uFlags As SHGFI_flags) As Long

' Frees memory allocated by the shell (pidls)
Private Declare Sub CoTaskMemFree Lib "ole32.dll" (ByVal pv As Long)


' Watch for shell changes
Public Sub StartWatch(ByVal hWnd As Long)

    ' Subclass the Form1 and get the current proc handle
    iOldProc = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf WindowProc)
    ' Set the watch messages routine
    SHNotify_Register hWnd

End Sub

' Stop watching shell messages
Public Sub StopWatch(ByVal hWnd As Long)
    
    ' Destroy our watch messages routine
    SHNotify_Unregister
    ' Give process back to the system and restore the original handle
    SetWindowLong hWnd, GWL_WNDPROC, iOldProc

End Sub

' Registers the shell change notification
Private Sub SHNotify_Register(hWnd As Long)
  
  Dim PS As PIDLSTRUCT
  
    ' If we don't already have a notification going
    If iSHNotify = 0 Then
        ' Get the pidl for the desktop folder.
        iDesktopPidl = GetDesktopPIDL(hWnd)
        ' If we have got the Desktop's PIDL
        If iDesktopPidl Then
            ' Fill the PIDLSTRUCT, we're watching
            ' desktop and all of the it's subfolders
            PS.pidl = iDesktopPidl
            PS.bWatchSubFolders = True
            ' Register the notification, specifying that we want the dwItem1
            ' and dwItem2 members of the SHNOTIFYSTRUCT to be pidls.
            iSHNotify = SHChangeNotifyRegister(hWnd, _
                            SHCNF_TYPE Or SHCNF_IDLIST, _
                            SHCNE_ALLEVENTSD Or SHCNE_INTERRUPT, WM_SHNOTIFY, 1, PS)
            ' If we could not get the Desktop's PIDL
            Else
            ' Free resources
            CoTaskMemFree iDesktopPidl
        End If
    End If
  
End Sub

' Unregisters the shell change notification
Private Sub SHNotify_Unregister()
  
   ' If we have a registered notification handle
    If iSHNotify Then
       ' Unregister it. If the call is successful, zero the handle,
       ' free and zero the desktop's pidl.
        If SHChangeNotifyDeregister(iSHNotify) Then
            iSHNotify = 0
            Call CoTaskMemFree(iDesktopPidl)
            iDesktopPidl = 0
        End If
    End If

End Sub

' Returns the Desktop's PIDL
'
'   hWnd - handle of window that will own any displayed msg boxes
'
' Called from SHNotify_Register
Private Function GetDesktopPIDL(hWnd As Long) As Long
  
  Dim iPIDL As Long
  
    ' Get the PIDL
    If SHGetSpecialFolderLocation(hWnd, 0, iPIDL) = 0 Then
        GetDesktopPIDL = iPIDL
    End If

End Function

' Returns a path from an absolute iPIDL (relative to the desktop)
' on success, or an empty string otherwise.
Private Function GetPathFromPIDL(ByVal iPIDL As Long) As String
  
  Dim sPath As String * MAX_PATH
  
    If SHGetPathFromIDList(iPIDL, sPath) Then
        GetPathFromPIDL = GetStrFromBufferA(sPath)
    End If

End Function

' Returns the string before first null char encountered (if any) from an ANSII string.
Private Function GetStrFromBufferA(ByVal sString As String) As String
    
    If InStr(sString, vbNullChar) Then
        GetStrFromBufferA = Left$(sString, InStr(sString, vbNullChar) - 1)
        Else
        ' If sString had no null char, the Left$ function
        ' above would return a zero length string ("").
        GetStrFromBufferA = sString
    End If

End Function

' Returns the Path for a specified full file path and name. The string
' is always terminated by a "\" char. On error returns vbNullString.
'
' Called from Form1.UpdateControl
Public Function GetFilePath(ByVal sPathName As String) As String

  On Error Resume Next
    
  Dim i As Long

    ' Error handling
    ' Remove any "\" char from the last position
    If Right$(sPathName, 1) = SEPARATOR Then
        sPathName = Left$(sPathName, Len(sPathName) - 1)
    End If
    
    For i = Len(sPathName) To 1 Step -1
        If Mid$(sPathName, i, 1) = SEPARATOR Then
            GetFilePath = Left$(sPathName, i)
          Exit For
        End If
    Next

End Function

' Returns the Filename for a specified full file path and name.
' On error returns vbNullString.
'
' Called from Form1.UpdateControl
Public Function GetFileName(ByVal sPathName As String) As String

  On Error Resume Next
    
  Dim i As Long

    ' Error handling
    ' Remove any "\" char from the last position
    If Right$(sPathName, 1) = SEPARATOR Then
        sPathName = Left$(sPathName, Len(sPathName) - 1)
    End If
    
    For i = Len(sPathName) To 1 Step -1
        If Mid$(sPathName, i, 1) = SEPARATOR Then
            GetFileName = Right$(sPathName, Len(sPathName) - i)
          Exit For
        End If
    Next

End Function

' Custom procedure to process the messages
Public Function WindowProc(ByVal hWnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
  
  Static prevEventID As Long    ' The previous event ID
  Static prevItem1 As String    ' The previous Item1 info
  Static prevItem2 As String    ' The previous Item2 info
  
  Dim sInfoA As String          ' dwItem1 notification info
  Dim sInfoB As String          ' dwItem2 notification info
  Dim SHN As SHNOTIFYSTRUCT
    
    ' Shell change notifications
    If uMsg = WM_SHNOTIFY Then
        DoEvents
        ' Fill the SHNOTIFYSTRUCT from it's pointer
        MoveMemory SHN, ByVal wParam, Len(SHN)
        ' lParam is the ID of the notication event
        Select Case lParam
            ' SHCNE_CREATE, SHCNE_DELETE
            '       SHN.dwItem1 is the PIDL(s) of the changed item(s)
            '       SHN.dwItem2 is not used
            Case SHCNE_CREATE, SHCNE_DELETE
                If SHN.dwItem1 Then
                    ' Get the Item's Path from its PIDL
                    sInfoA = GetPathFromPIDL(SHN.dwItem1)
                    ' As duplicate notifications occur, we check the previous event
                    ' If the notification is a new one
                    If ((prevEventID <> lParam) Or (prevItem1 <> sInfoA)) Then
                        ' Inform the app that the control may need to be refreshed
                        Call Form1.UpdateControl(lParam, sInfoA, vbNullString)
                    End If
                End If
                
            ' SHCNE_RENAMEITEM
            '       SHN.dwItem1 is the previous PIDL or name of the item.
            '       SHN.dwItem2 is the new PIDL or name of the item.
            Case SHCNE_RENAMEITEM
                If SHN.dwItem1 And SHN.dwItem2 Then
                    ' Get the Item's Path from its PIDL
                    sInfoA = GetPathFromPIDL(SHN.dwItem1)
                    ' Get the Item's Path from its PIDL
                    sInfoB = GetPathFromPIDL(SHN.dwItem2)
                    ' As duplicate notifications occur, we check the previous event
                    ' If the notification is a new one
                    If ((prevEventID <> lParam) Or (prevItem1 <> sInfoA) Or (prevItem2 <> sInfoB)) Then
                        ' Inform the app that the control may need to be refreshed
                        Call Form1.UpdateControl(lParam, sInfoA, sInfoB)
                    End If
                End If
            
            ' SHCNE_ATTRIBUTES
            '       SHN.dwItem1 is the PIDL(s) of the changed item(s)
            '       SHN.dwItem2 is not used
            Case SHCNE_ATTRIBUTES
                If SHN.dwItem1 Then
                    ' Get the Item's Path from its PIDL
                    sInfoA = GetPathFromPIDL(SHN.dwItem1)
                    ' As duplicate notifications occur, we check the previous event
                    ' If the notification is a new one
                    If ((prevEventID <> lParam) Or (prevItem1 <> sInfoA)) Then
                        ' Inform the app that the control may need to be refreshed
                        Call Form1.UpdateControl(lParam, sInfoA, vbNullString)
                    End If
                End If
        End Select
        
        ' Store the events details for duplicate notifications
        prevEventID = lParam
        prevItem1 = sInfoA
        prevItem2 = sInfoB
    End If
    
    ' System processes the message
    WindowProc = CallWindowProc(iOldProc, hWnd, uMsg, wParam, lParam)
  
End Function

######################## CODE END #############################





Run the project, make any changes(rename, delete) to a file currently displayed in Thumbnailer or drag items from Thumbnailer and drop them anywhere with a Move action. 

Thumbnailer will refresh its contents to show any changes.