This function returns the current system modal window.

#define INCL_WINWINDOWMGR /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HWND    hwndDesktop;   /*  Desktop-window handle. */
HWND    hwndSysModal;  /*  Handle of system modal window. */

hwndSysModal = WinQuerySysModalWindow(hwndDesktop);