This macro sets the text for Menu indexed item to buffer.

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

HWND      hwndMenu;  /*  Menu window handle. */
USHORT    usId;      /*  Identity of the menu item. */
PSZ       pText;     /*  Text for the menu item. */
BOOL      rc;        /*  Success indicator. */

rc = WinSetMenuItemText(hwndMenu, usId, pText);