🚀 go-pugleaf

I have been trying to use GetClientRect function with no success.
I hope somebody can explain what I have been doing wrong.  The code 
is given below (hWnd is actually a child window, a menu item similar
to the Word-for-Windows' menu below the standard menu bar).  Thanks.

long FAR PASCAL menu_proc (HWND hWnd, unsigned iMessage,
                        WORD wParam, LONG lParam)
{
    HDC hDC;
    LPRECT lpRect;

    switch (iMessage)
    {
            ...
       case WM_RBUTTONDOWN:
            GetClientRect (hWnd, lpRect);  /* <<-- this is where it bombs */
            hDC = GetDC (hWnd);            /* out; */
            InvertRect (hDC, lpRect);      
            ReleaseDC (hWnd, hDC);
            break;
            ...
    };

}