Private Declare Function GetParent Lib "user32.dll" ( _
   ByVal hwnd As Long) As Long
 
Private Declare Function WindowFromPoint Lib "user32.dll" ( _
   ByVal xPoint As Long, _
   ByVal yPoint As Long) As Long
 
Private Declare Function GetCursorPos Lib "user32.dll" ( _
   lpPoint As POINTAPI) As Long
 
Private Type POINTAPI
  X As Long
  Y As Long
End Type
 
Private Declare Function SetLayeredWindowAttributes Lib "user32.dll" _
    (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, _
    ByVal dwFlags As Long) As Long
 
Private Declare Function GetWL Lib "user32" Alias "GetWindowLongA" _
    (ByVal hwnd As Long, ByVal nIndex As Long) As Long
 
Private Declare Function SetWL Lib "user32" Alias "SetWindowLongA" _
  (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNL As Long) As Long
 
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)
  Private Const WS_L = &H80000
  Private Const GW_E = -20
  Private Const LWA_1 = &H2
  Private Const LWA_2 = &H1
 
Public Function SetTrans(ByRef tForm As Form, _
    ByVal iTrans As Byte, Optional ByVal iTune As Boolean = True) As Boolean
    On Error Resume Next
    Dim LWL As Long
    Err = 0
    If iTune Then
        LWL = GetWL(tForm.hwnd, GW_E)
        LWL = LWL Or WS_L
        SetWL tForm.hwnd, GW_E, LWL
    End If
    SetLayeredWindowAttributes tForm.hwnd, RGB(255, 0, 255), iTrans, LWA_1 Or _
      LWA_2
    SetTrans = Err = 0
  End Function
 
Function GetParentHandle(ByVal Handle As Long) As Long
  On Error Resume Next
  GetParentHandle = Handle
     Handle = GetParent(Handle)
    If Handle = 0 Then Exit Function
  If Handle = hwnd Then Exit Function
     GetParentHandle = GetParentHandle(Handle)
End Function
 
Private Sub Form_Load()
Timer1.Interval = 100
  Timer1.Enabled = True
  Me.Show
  SetTrans Me, 150, True ' Transparenz der Form festlegen (Wert zwischen 
  ' 0=unsichtbar und 255=sichtbar)
End Sub
 
Private Sub Timer1_Timer()
 Dim C As POINTAPI, lRet As Long, lHandle As Long
 lRet = GetCursorPos(C)
  lHandle = WindowFromPoint(C.X, C.Y)
    If Not GetParentHandle(lHandle) = hwnd Then
SetTrans Me, 90, True ' Transparenz der Form festlegen
 End If
End Sub
 
Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y _
  As Single)
SetTrans Me, 255, True ' Transparenz der Form festlegen
End Sub