This example uses WinPeekMsg to count the total number of pending messages for the window corresponding to hwndFilter.

#define INCL_WINMESSAGEMGR      /* Window Message Functions     */
#define INCL_WINWINDOWMGR       /* Window Manager Functions     */
#include <os2.h>

HAB     hab;            /* anchor-block handle                  */
QMSG    qmsg;           /* message                              */
HWND    hwndFilter;     /* message queue filter                 */
ULONG   flOptions;      /* peek options                         */
ULONG   ulMsgCount=0;   /* message count                        */

/* don't remove messages */
flOptions = PM_NOREMOVE;

/* count number of messages for filter window */
while (WinPeekMsg (hab, &qmsg, hwndFilter, 0, 0, flOptions))
   ulMsgCount++;