Subclassing...wheres my error?!

[iawix]

Alright, I've made a program that uses several hotkeys. To do this, I implemented subclassing. When I exit the program, I get an error...

I have the SetWindowLong() codes inside a form that is active the whole program, but the program starts with a Sub Main().

The referenced procedure is in a module, as advised. Code is as follows:

Public Function CheckMessage(ByVal hWnd As Long, ByVal uMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
    Select Case uMsg
        Case WM_HOTKEY
            HotKeyPress wParam
            CheckMessage = 1
            Exit Function
        Case Else
            CheckMessage = CallWindowProc(PrevProc, hWnd, uMsg, wParam, lParam)
    End Select
End Function

When I use the hotkey CTRL-SHIFT-F5 my program ends. As I unload the form I'm using in the module, the form initiates the code:

SetWindowLong frmOptions.hWnd, GWL_WNDPROC, PrevProc

And then the program ends.

Any ideas where the error might be coming from?

Thanks a bunch in advance,
-Steve