How to set Callback's return value from called procedure?

[E B Knoppert]

This is what i would like to do;
I know the alternatives using extra variable(s) but i would like it this way.
Just a simple flag 0 or 1 to skip DefWindowProc() but also set a new return value.
This way i can write code more easily and in 1 single line.

Function CallMySetCursorFunction( ByVal hWnd as Long, RetVal As Long PTR ) As Long
 
    FUNCTION = 1
 
    @RetVal = %Whatever
 
End Function
 
Function wnd_Proc( ByVal hWnd AS LONG, ByVal wMsg AS LONG, ByVal wParam AS LONG, ByVal lParam AS LONG )  As LONG
 
    Select Case wMsg
    Case %WM_SETCURSOR
 
        If CallMySetCursorFunction( hWnd, VarPtr( FUNCTION ) ) Then Exit Function
 
    End Select
 
    FUNCTION = DefWindowProc( hWnd, wMsg, wParam, lParam )
 
End Function