This function returns the state (checked/not checked) of the identified menu item.

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

HWND      hwndMenu;  /*  Menu window handle. */
USHORT    usId;      /*  Identity of the menu item. */
BOOL      rc;        /*  Checked-state indicator. */

rc = WinIsMenuItemChecked(hwndMenu, usId);