Menu:DisableItem(nItemID,lSubMenu): public: return true
  The menu item (pointed to with the nItemID pointer) selection is disabled.
  All code blocks are passed to nItemID, which is the offset to internal
  table of flags which indicates the recursive entering of the menu item.

  Parameter description:
  ~~~~~~~~~~~~~~~~~~~~~~
  nItemID: numeric: no default
   Menu item pointer.

  lSubMenu: logical: default is true
   If true, disabled are all items below the current item (it can have
   submenu selectable by hot key). If false, only the current item is
   selected.