AddItem()

         Adds a selectionable item to a submenu

    Syntax:

         AddItem( aMenu, nSubMenu, cItem, [cMess], [nPos] ) -> Nil

         aMenu    : The menu created with NewMenu()
         nSubMenu : The submenu's number where add the item
         cItem    : The item to add to the submenu
         cMess    : The message of the item
         nPos     : The position of the item in the submenu.
                    Last position if null.

    Description:

         Adds a item to a submenu, activing the item as selectionable.


    Return:

         Nothing.

    Example:

         aMenu := NewMenu( { "^System", "^Tools", "^Other" }, ;
                           { "N/W", "R/W", "W/B",  "W+/B", ;
                             "N/W", "W/B", "N+/W", "R/W", "GR+/B" } )
         AddItem ( aMenu, 1, "Item ^1", "Message" )