This function starts or stops a window flashing.

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

HWND    hwndFrame;  /*  Handle of window to be flashed. */
BOOL    fFlash;     /*  Start-flashing indicator. */
BOOL    rc;         /*  Success indicator. */

rc = WinFlashWindow(hwndFrame, fFlash);