View posts since last visit

Im not to sure if this would work as ive never tried it, but i suppose there's no harm in me sharing my idea-which is very rough.

Using global.asa you could have a function in session_onEnd that adds the current time and date to a field in the table that holds the users username etc.

Then when they log in this field would be queried then another query would be executed to find posts after that date and time.

However this method wouldn't be exact as depending on when the user leaves the site and when the session terminates there could be up to a couple of minutes. To rectify this you could shorten the session time.