The SetMenuDefaultItem function sets the default menu item for the specified menu.
BOOL SetMenuDefaultItem(
  HMENU hMenu,  
  UINT uItem,   
  UINT fByPos   
);
 If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error information, use the GetLastError function.
  Windows NT: Requires version 4.0 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in winuser.h.
  Import Library: Use user32.lib.
Menus Overview, Menu Functions, GetMenuDefaultItem