' zunächst die benötigten API-Deklarationen
Private Declare Function GetDesktopWindow Lib "user32" _
  () As Long
 
Private Declare Function SendMessage Lib "user32" _
  Alias "SendMessageA" (ByVal hWnd As Long, _
  ByVal wMsg As Long, ByVal wParam As Long, _
  lParam As Long) As Long
 
Private Declare Function GetClientRect Lib "user32" _
  (ByVal hWnd As Long, lpRect As cRECT) As Long
 
Private Declare Function RedrawWindow Lib "user32" _
  (ByVal hWnd As Long, lprcUpdate As cRECT, _
  ByVal hrgnUpdate As Long, ByVal fuRedraw As Long) _
  As Long
 
Private Const WM_SETREDRAW = &HB
Private Const RDW_INVALIDATE = &H1
Private Const RDW_ALLCHILDREN = &H80
Private Const RDW_UPDATENOW = &H100
Private Const RDW_ERASE = &H4
 
Private Type cRECT
  left As Long
  top As Long
  right As Long
  bottom As Long
End Type

Private Sub UpdateDesktop()
  Dim hWndDesktop As Long
  Dim R As cRECT
 
  ' Fensterhandle des Desktops ermitteln
  hWndDesktop = GetDesktopWindow()
 
  SendMessage hWndDesktop, WM_SETREDRAW, True, 0&
  GetClientRect hWndDesktop, R
  RedrawWindow hWndDesktop, R, 0&, RDW_ERASE Or _
    RDW_INVALIDATE Or RDW_ALLCHILDREN Or RDW_UPDATENOW
End Sub

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