CS5 - Rollover Image control based upon the URL

Using CS5 and have a template set up with rollovers for navigation:
Does anyone knows how to change the rollover image to display the "highlighted" image when you're on that specific page?

Example: Pages 1 thru 6 have rollover navigation on the left side of a template (so same coding used thoughout the site). Standard image changes with mouseover for selecting the new page. What I would like is to have the "mouseover image" for page 4 displayed when you're actually on page 4 ... etc for other pages.

Can that be done using a template? I know I can do it if I create "non template based" pages.