The following code illustrates how to provide default behavior for a secondary window.

 #define INCL_SW
 #include <os2me.h>

 MRESULT MyDlgProc (HWND hwnd, ULONG msg, MPARAM mp1, MPARAM mp2)
 {
    switch (msg) {

    }

    /* Call WinDefSecondaryWindowProc for default processing */
    return (WinDefSecondaryWindowProc (hwnd, msg, mp1, mp2));

 }