Here's is test project that should work.

 

uploads/20100129_124724_Transparency.zip 

 

Private Const GWL_EXSTYLE = (-20)
Private Const WS_EX_LAYERED = &H80000
Private Const LWA_ALPHA = &H2

 

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 SetLayeredWindowAttributes Lib _
    "User32" (ByVal hwnd As Long, ByVal crKey As Long, _
    ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
   
Public Function TransForm(Form As Form, TransLevel As Byte) As Boolean

 

On Error Resume Next
   
    SetWindowLong Form.hwnd, GWL_EXSTYLE, WS_EX_LAYERED
    SetLayeredWindowAttributes Form.hwnd, 0, TransLevel, LWA_ALPHA
   
    TransForm = Err.LastDllError = 0
   
End Function

 

 

TransForm Me, 1

 

That should make your form transparent.

 

TransForm Me, 255

 

To reverse the transparency

 

If it barks at you, pass the number as a byte: CByte(255)

 

 

Did you try again? It really does work with code in activate and deactivate event.

 

If you have DockingPanes and you click on PaneCaption it doesn't anymore

 

 

I tried again and it seems that DockingPanes is causing this behaviour. If you click on one of the pane captions the form is grayed. Clicking somewhere else on other form seems to work fine.

 

 

 

 

You could use Form Activate and Deactivate event and set desired transparency. I tried it myself but sometimes form will loose it transparency entirely and only showing a "grayish shadow" and after resizing form repaints itself and everything is back to normal. Don't know why but is does...