Private Declare Function CreateRectRgn Lib _
"gdi32" (ByVal X1 As Long, ByVal Y1 As Long, _
ByVal X2 As Long, ByVal Y2 As Long) As Long
Private Declare Function CombineRgn Lib _
"gdi32" (ByVal hDestRgn As Long, ByVal hSrcRgn1 As Long, _
ByVal hSrcRgn2 As Long, ByVal nCombineMode As Long) As Long
Private Declare Function SetWindowRgn Lib _
"user32" (ByVal hWnd As Long, ByVal hRgn As Long, _
ByVal bRedraw As Boolean) As Long
Private Declare Function DeleteObject Lib _
"gdi32" (ByVal hObject As Long) As Long
' Constants used by the CombineRgn function
Private Const RGN_AND = 1
Private Const RGN_OR = 2
Private Const RGN_XOR = 3
Private Const RGN_DIFF = 4
Private Const RGN_COPY = 5

Private Sub Form_Activate()
Dim rgnForm As Long, rgnCombined As Long
Dim rgnControl As Long, x As Long
Dim formWidth As Single, formHeight As Single
Dim borderWidth As Single, titleHeight As Single
Dim ctlLeft As Single, ctlTop As Single
Dim ctlWidth As Single, ctlHeight As Single
Dim ctl As Control
' Calculate the form area
borderWidth = (Me.Width - Me.ScaleWidth) / 2
titleHeight = Me.Height - Me.ScaleHeight - borderWidth
' Convert to Pixels
borderWidth = ScaleX(borderWidth, vbTwips, vbPixels)
titleHeight = ScaleY(titleHeight, vbTwips, vbPixels)
formWidth = ScaleX(Me.Width, vbTwips, vbPixels)
formHeight = ScaleY(Me.Height, vbTwips, vbPixels)
' Create a region for the whole form
rgnForm = CreateRectRgn(0, 0, formWidth, formHeight)
rgnCombined = CreateRectRgn(0, 0, 0, 0)
' Make the graphical area transparent by combining the two regions
x = CombineRgn(rgnCombined, rgnForm, rgnForm, RGN_DIFF)
' Make the controls visible
For Each ctl In Controls
' Make the regions of controls whose container is the form visible
If TypeOf ctl.Container Is Form Then
ctlLeft = ScaleX(ctl.Left, vbTwips, vbPixels) + borderWidth
ctlTop = ScaleX(ctl.Top, vbTwips, vbPixels) + titleHeight
ctlWidth = ScaleX(ctl.Width, vbTwips, vbPixels) + ctlLeft
ctlHeight = ScaleX(ctl.Height, vbTwips, vbPixels) + ctlTop
rgnControl = CreateRectRgn(ctlLeft, ctlTop, ctlWidth, ctlHeight)
x = CombineRgn(rgnCombined, rgnCombined, rgnControl, RGN_OR)
End If
Next ctl
' Set the clipping area of the window using the resulting region
SetWindowRgn hWnd, rgnCombined, True
' Tidy up
x = DeleteObject(rgnCombined)
x = DeleteObject(rgnControl)
x = DeleteObject(rgnForm)
End Sub