This function inspects the thread's message queue and returns to the application with or without a message.

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

HAB      hab;         /*  Anchor-block handle. */
PQMSG    pqmsg;       /*  Message structure. */
HWND     hwndFilter;  /*  Window filter. */
ULONG    ulFirst;     /*  First message identity. */
ULONG    ulLast;      /*  Last message identity. */
ULONG    flOptions;   /*  Options. */
BOOL     rc;          /*  Message-available indicator. */

rc = WinPeekMsg(hab, pqmsg, hwndFilter, ulFirst,
       ulLast, flOptions);