VB Forum / Win API / April 2007

I'm a bit new to subclassing and here is what I'm trying to do.

I have an application which reads data from two other windows, called
Trade1 and Trade2.  I use some OCR stuff which basically scraps those
screens for data.

Now, everything works fine, but I have a problem in that I have a very
annoying 'flicker' happening.

What I'm trying to do, is to subclass API SendMessage to prevent the
flicker on the 2 windows (Not my current VB6 Application).  I want the
Trade1 and Trade2 Windows to never get focus, but to allow scraping if
required).

Here is what I've got so far:
Code from :  http://www.developerfusion.co.uk/show/49/2/

'// variable that stores the previous message handler
Public ProcOld As Long
Public Const GWL_WNDPROC = (-4)
'// Windows API Call for catching messages
Public Declare Function SetWindowLong Lib "user32" Alias
"SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal
dwNewLong As Long) As Long
'// Windows API call for calling window procedures
Public Declare Function CallWindowProc Lib "user32" Alias
"CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hwnd As Long,
ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As
Long

Public Function WindowProc(ByVal hWnd As Long, ByVal iMsg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long
   Select Case iMsg
   Case else
       '// Ignore all messages for the moment
   End Select
   '// pass all messages on to VB and then return the value to
windows
   WindowProc = CallWindowProc(procOld, hWnd, iMsg, wParam, lParam)
End Function

Form Code

'// form_load event. Catch all those messages!
Private Sub Form_Load()
   On Error Resume Next
   '// saves the previous window message handler. Always restore this
value
   '// AddressOf command sends the address of the WindowProc
procedure
   '// to windows
   ProcOld = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf WindowProc)
End Sub

'// form_queryunload event. Return control to windows/vb
Private Sub Form_Unload(Cancel As Integer)
   '// give message processing control back to VB
   '// if you don'//t do this you WILL crash!!!
   Call SetWindowLong(hWnd, GWL_WNDPROC, procOld)
End Sub

' --------------------------------------------

However, the above code only seems to set the trapping within the
current application.
I've been trying all day to modify the above code and get it to also
allow me to intercept the messages on Trade1 and Trade2 window, but so
far no luck.

Is what I'm trying to do possible, and can the above code be modified
to make this happen?