This function causes modal WinProcessSecondaryWindow or WinSecondaryWindow calls to return.

#define INCL_SW
#include <os2.h>

HWND     hwndDlg;   /*  Secondary dialog window. */
ULONG    ulResult;  /*  Result. */
BOOL     rc;        /*  Return codes. */

rc = WinDismissSecondaryWindow(hwndDlg, ulResult);