ok, that makes more sense. You could try the following:
when they click submit, the form does two things.
1. Opens a popup window that says you are now being redirected to. . . (in the background, this is a php script that mails you their form submission)
2. Sends the visitor to paypal's site in the original window with the post form fields.
the other thing you may try is when they hit submit, they get taking to a php script where you email the submission to yourself, then there you have the same form except with hidden input fields and all the values already filled in, and somehow using javascript, submit the form on the redirect to paypal's site. Not quite sure how to do the javascript for that, but if you post on a javascript forum i'm sure someone would be able to help with that.
Hope this helps.
Cgraz