NEWBIE COOKIE PROBLEM

Hi, I am now stuck with some problem associated with setcookie. I essentially was looking for a method of preventing two users logging in from the same machine. I was planning to do it by setting the cookie to be sent to all requests from the IP of my machine and setting the cookie's life time to the session duration. setcookie("cookie_user", "arun","", "/","IP Address"); However, this doesnt seem to be happening. If i set the time of expiry to time()+3600 then it works fine i can recognise is any user has already logged in. How do i make the cookie available to all requests from a particular machine and the lifetime restricted to the session length of the session that set the cookie. Any help! Thanks Arun TickleWit.com Pvt Ltd 0 98300 24824 91 33 3574692