This macro sets the check state of the specified menu item to the flag.

#define INCL_WINWINDOWMGR /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HWND      hwndMenu;  /*  Menu window handle. */
USHORT    usId;      /*  Item identifier. */
BOOL      fCheck;    /*  Check flag. */
BOOL      rc;        /*  Success indicator. */

rc = WinCheckMenuItem(hwndMenu, usId, fCheck);