Mirror url

Hi, My client wants an affiliate system developed. I already have an affiliate system that works, but I need to extend it a little. My client want that the affiliate like should be something like: www.domain.com/rosegarden where rosegarden is the affiliates choosen affiliate tracking. 1. I have a script that creates the folder rosegarden and copy index.php file into that folder that contains the tracking script and then just redirect them back to www.domain.com <http://www.domain.com/> 2. I can use ModRewrite or something like that. But I have never used that before, and I am curious of how difficult it would be to create a dynamic system for this. When the affiliate signs up they can choose their subfolder and the system will automatically create necessary files and copy them. Am I clear of what I want to accomplish? Best regards, Peter Lauri