Ajax for Credit Card Processing


I have a web app that accepts credit card payments.

I want to use AJAX to do an asynchronous post to the server and process the
payment. I am using the UpdateProgress control to show a progress indicator.

Two questions:

1) If the user clicks the button more twice will the payment be processed
twice? I performed a test where I just added text to a lable in the same
UpdatePanel as the button and the text did not "double up" when I clicked
the Submit button twice. So it "seems" as though the payment wouldn't be
process twice. And,

2) Is there a way to "Lock" the screen so that the user can't click the
Submit button more than once (in the event that my assumption in #1 is

Thanks in advance,