I've got a donation form for a uk charity - they have a drupal module that accepts paypal ipn donations, but they want to record any attempt to donate then use the IPN to to update a record when it's completed.
The problem I have come across is that Paypal expect the donation form to be submitted straight to them
http://www.paypal.com/cgi-bin/webscr.
What I need to to is intercept the submission so I can created a database record before the user hits paypal.