Chat script with admin section

Hi bidders, I need a chat script to be done immediately with admin panel which should be capable of handling 20000 users. Features When chat script is in minimized state and if there are any new messages,yellow light should glow like gtalk or yahoo to intimate new message arrival User section: It should be protected by login Admin section: Admin must be the only person to communicate with the person he likes Budget:(30-50$) Needed to see a live demo before i select the bidder Regards ashwin