Chatting online with Joomla - Urgent

I would like to add a live, instant-message chat feature to my Web site, which is based on Joomla software. The IM chat would work something like Facebook o r AOL in that people would be able to chat in real time. But the IM feature needs to be customized in a few ways. I have both "users" and " members" . The users CANNOT chat with users. But users can chat with member only. 1. I don't want users to be able to chat with other users. Users can only chat with the members. So I want to block name list of users . Show just member list name only. .2 Everyone (both users and members) would have to register and sign in to use the IM chat feature. However, the chat should work only one-way. Members won't be able to see which users are online since users will not have pics (only members will have pics). But the member will be able to see the user's registered screen name (only) when he/she receives an IM. Essentially, this is a live but not a social IM chat system. 3. I want the users to be able to see a list of members who are online at any time (as on the Facebook chat function), but I don't want the users to be able to see all members online because that could be a very long list of people in the box. Instead, I want to show just the members in he specific area where the users have searched by city/state or zip code.