Flash video chat

I just finished the following tutorial and it works just great!

http://www.macromedia.com/devnet/flashcom/articles/first_comm_app.html

what I want now is:

To have just 1 person with a camera and multiple users watching him and chatting with him and one with the other.

So I left only the 1 AvPresence component and the first user who comes in the site/chatroom and has a camera is the one who will be watched. How can I make a safer way so only one person will be able to show himself and all the others, using a login just watch and chat?

I hope all these are understandable.
Thanks all.