put a class (we'll say class="topnav") on the cells that have the nav items, then use the following code in the style portion of your head, or in a css file.
Code:
a.topnav:hover, a.topnav:visited:hover { border-right:2px solid blue; }
a.topnav:link, a.topnav:visited { border-right:2px solid red; }
That should do it for you.