Database insert/update from Browser Refresh or Back/Forward Button

Hi! Went Google surfing on Browser Refresh & Back/Forward Button and it turned out that PHP can do the dirty work. Problem is no sample script, all I see are comments about suggesting on using the $_SESSION or the database to check the $_POST stuffs and do something about it. So does anyone know of a good sample code to help this out? Like classes or something because manually writing it on 20+ webpages is a haunting task for the billing stuffs I had already developed for 6 months. Beside I don't really have an concept of writing a good "Refresh/Back/Forward" detections script. Thanks, FletchSOD