PHP Script to auto-rotate leads into a database

My website will be running an online advertising co-op and will have anywhere from 10-60 participants each contributing their money into the co-op. I need to have a script that will automatically rotate and disburse leads that come in off of the main website to a database of email addresses? (the people that are in the advertising co-op) A lead would be considered anyone who was on the site who filled out either a 'Contact Us' form or a 'Free Analysis' form. Perhaps even having it distribute leads according to how many shares were purchased out of the co-op. The most important thing is that it is evenly disbursing leads to all of the shareholders of the co-op.