creating multiple sessions

Hi, I've encountered a situation where I need to have two or more SEPARATE sessions running in separate windows. The reasons are complicated, so I'll keep things simple by just explaining the problem! Unfortunately my understanding of sessions is a little sketchy at best so please stick with me... As I understand it, you can start a new session by manually opening another separate Internet Explorer window, but I wish the new session to start in a window I've opened automatically from a previous page. Unfortunately this appears to carry on the session from the source window, which I don't want - I want a new, separate session. I've considered calling session_start(); in the new window, then destroying the session and calling session_start(); to start a new, separate session, but surely this will destroy the session in the original window, which I want to keep intact! So put simply, is there anyway to 'force' a new session? Thanks, John