Automatic affiliate linking

I have a website that is user driven. Users come to my site and post a deal they found elsewhere on the internet. I am signed up with affiliates, but right now have to insert my affiliate link by hand. I would like someone to help set up an automatic redirect so that whenever someone posts a link to a product, my affiliate link gets inserted automatically (preferably cloaked). My website uses vbulletin. Would prefer someone who has experience with this,and who can do it quickly.