Restricting Internet Sharing (sharing ethernet connection with ap)


I am attempting to restrict who can connect to my mac mini's airport in order to access it's ethernet connection. I do not want to do this via encryption however but rather by:
1. Restricting the mac addresses that can connect.
2. (preferrably) When a user connects, they are presented with a webpage that requests they log in.

Has anyone ever done anything similar to this? I know I have seen that application that allows you to do this with an actual airport unit however I want to use the airport card that is built into my mini.

Programming/scripting something will not be a problem.