WinRequestMutexSem requests ownership of a mutex semaphore or waits for a Presentation Manager message.

#define INCL_WINMESSAGEMGR
#include <os2.h>

HMTX      hmtx;       /*  The handle of the mutex semaphore to request. */
ULONG     ulTimeout;  /*  Time-out in milliseconds. */
APIRET    ulrc;       /*  Return Code. */

ulrc = WinRequestMutexSem(hmtx, ulTimeout);