membership plugin and affiliate programs

I am trying to set up an affiliate program on a WPMU installation wtih BP and the membership plugin. I am usint affiliate pro, it seems to have more features than the WP affiliate program for my use. I am, however, running into a problem installing the code onto a page - as the membership plugin and registration pages are simply a single page (including the thank you page). any chance someone can help me with where to place this unique code on a unique page so that it will track registrations?