This function hides the modeless dialog window, and causes WinProcessDlg or WinDlgBox to return.

#define INCL_WINDIALOGS /* Or use INCL_WIN, INCL_PM, Also in COMMON section */
#include <os2.h>

HWND     hwndDlg;   /*  Dialog-window handle. */
ULONG    usResult;  /*  Reply value. */
BOOL     rc;        /*  Dialog-dismissed indicator. */

rc = WinDismissDlg(hwndDlg, usResult);