Nav bar -- highlighted by current div

Nav bar -- highlighted by current div

I have a navbar numbered 1 thru 6 for a slider.  You can see it here. http://gtwebconcepts.com/tim/

Is there a way to have the current navigation number share the rollover state?  In other words, if I slide to #4 then the actual navbar #4 displays in a different color until I navigate away from it.  I originally thought that this would be a simple CSS thing, but that idea went more towards javascript 'test'.  Then I wondered if there might be a plug-in for this sort of thing.

Any thoughts?