This macro expands to:

#define WinCheckMenuItem(hwndMenu, usId, fCheck)
   ((BOOL)WinSendMsg(hwndMenu,
                     MM_SETITEMATTR,
                     MPFROM2SHORT(usId, TRUE),
                     MPFROM2SHORT(MIA_CHECKED, (BOOL)(fCheck) ? MIA_CHECKED : 0)))

This function requires the existence of a message queue.