It's possible but not vb or HTML friendly and would last only as long as the timeout UNLESS it is phpchat. If it's java based chat then it would be quite difficult and would require a few tweaks.

Chris is right, you can't code the instant that person closes the window UNLESS it is phpchat. When you are using an applet and after the user logs off, the server cannot detect online usage nor execute an sql process unless you use a metarefresh within a hidden/visible frame on the same page to keep the sql connection alive.

I'm not sure if you understand what I'm saying but I hope you understand what we were tryign to say.