This function waits for an event semaphore to be posted for a Presentation Manager message to be received.

#define INCL_WINMESSAGEMGR
#include <os2.h>

HEV       hev;        /*  The handle of the event semaphore to wait for. */
ULONG     ulTimeout;  /*  Time-out in milliseconds. */
APIRET    rc;         /*  Return Code. */

rc = WinWaitEventSem(hev, ulTimeout);