Private Delegate Function SubWndProcDelegate(ByVal hWnd As IntPtr, ByVal msg As  
_ Int32, ByVal wParam As Int32, ByVal lParam As IntPtr) As Int32

Private Declare Function SetWindowLong Lib "user32.dll" Alias "SetWindowLongA" _
        (ByVal hWnd As IntPtr, ByVal nIndex As Int32, ByVal dwNewLong As _
        SubWndProcDelegate) As IntPtr
 
Private Declare Function CallWindowProc Lib "user32.dll" Alias _
  "CallWindowProcA" _
        (ByVal lpPrevWndFunc As IntPtr, ByVal hWnd As IntPtr, ByVal msg As _
        Int32, _
        ByVal wParam As Int32, ByVal lParam As Int32) As Int32

Private Function SubWndProc( _
            ByVal hWnd As IntPtr, _
            ByVal msg As Int32, _
            ByVal wParam As Int32, _
            ByVal lParam As IntPtr) As Int32
 
        If msg = WM_COPYDATA Then
 
            Dim st As COPYDATASTRUCT = CType(Marshal.PtrToStructure(lParam, _
        GetType(COPYDATASTRUCT)), COPYDATASTRUCT)
            'returnString = st.lpData
            'returnValue = True
            'MessageBox.Show(st.lpData)
        End If
 
        ' Weiterreichen der Messages an Windows.
        ' Hier besteht auch die Möglichkeit,
        ' Meldungen zu unterdrücken, indem man
        ' sie nicht weiterleitet.
 
        Return CallWindowProc(m_intptrPrevWndProc, hWnd, msg, wParam, lParam)
    End Function