Database Extract ID

Maybe a simple question but baffling me a bit. What I am doing is spanning a form across several pages, I was going to use session variables to collect the data but there are some 23 questions which can be of various lengths in answer form so I have opted to fill in a database entry. Multiple users may be logging onto the site at any one time.

What I need to do is create just one session variable - the user_ID which is allocated once the first database entries are initially added.

The question:If I am doing an 'INSERT into tablename values 1, 2, 3, 4 (thus creating a new record) how can I automatically get the user_ID (which is an autonumber field in the database) straight back out and allocate it to a session variable?) - we are trying to avoid a 'login' procedure