Update record on Success page from PayPal

I understand that when using PayPal Standard that the checkout is not realtime and is processed by PayPal on a first in first procecessed fashion. I am good with that. I understand that you need an IPN to have PayPal talk to my website to do the neccessary updating. Not sure how all that works as of yet.

Here is what I would like to know if I can do and if someone can give me some direction. Once the customer goes through the checkout process, confirms the order (which stores the order and the "Order Status" as pending) they go to PayPal and finish the payment process. They are then redirected back to my website to the success page. Once this page is loaded I would like for it to reconize the customer and update the database of their "Order Status" to billed. I understand that the payment has not actually been processed yet, got it still good with that.

I am just exploring ideas at this point. In all the years I have delt with PayPal that if a customer paid through Pay Pal the payment as always gone through.

Thanks in advance.