I used ,
CMenu* pMenu = AfxGetMainWnd()->GetMenu();
if(pMenu != NULL)
{
for(UINT i = 0; i < pMenu->GetMenuItemCount (); ++i)
pMenu->EnableMenuItem(i, MF_BYPOSITION | MF_DISABLED);
}
as mentioned in http://forums.codeguru.com/showthread.php?456136-Can-I-disable-menu-bar. It worked for me.