<oListBox>:addItem(<cText> [, <expValue>]) --> self

        <cText> is a character string that indicates the item's text to
        display in the list.

        <expValue> is a value that is associated with the list item.  If
        omitted, the item's associated data will be NIL.

        addItem() is a method of the ListBox class that is used for appending
        a new item to a list.  When adding an item, an optional value may be
        included.  This enables you to associate pertinent data with the text
        displayed in the list.

        Note:  When present, the scroll bar is automatically updated to
        reflect the addition of the new item.