I would try JqueryjQuery, something like this:
$("#myDiv ul li:last-child").addClass("lastLi");
$("#myDiv ul li:last-child").addClass("lastLi"); You would need to make the lastLilastLi class set the lili border width to 0.
Here is a link to the JQuery last-childjQuery last-child selector documentation: http://docs.jquery.com/Selectors/lastChild