border                                       (Assignable)

        Contains an optional string that is used when drawing a border around
        the pop-up menu.  Its default value is B_SINGLE + SEPARATOR_SINGLE.
        The string must contain either zero or exactly eleven characters.
        The first eight characters represent the border of the pop-up menu
        and the final three characters represent the left, middle, and right
        characters for the menu item separators.  The eight characters which
        represent the pop-up menu border begin at the upper-left corner and
        rotate clockwise as follows:  upper-left corner, top, upper-right
        corner, right, bottom, bottom-left corner, and left.