Side column banner ad, rotating positions

[ken-cj]

Is there a plug-in or product for banner ads to be repositioned when members reload. Example, I have 20 ads in a side column and I want them to be reposition each time the page reloads. Below is a link to a site that does exactly what I need, but for the life of me I can not find out how to do this.

http://ls1tech.com/forums/


Thanks
Ken