I was hoping that someone may know how to accomplish this transition within the car ad that I found with actionscript. I can do this by making alot of masks within my FLA, but there has to be a faster way with Actionscript.

The website is here: http://www.cheapcarsearch.com/?hop=964rscs. The car banner at the top has a venetian blinds type transition. HOw is this done? Any help or guidance would be greatly appreciated. Thank you!