Integrate simple web page with Amazon Payments

I recently set up a basic web page that includes a form for Amazon payments. Currently I have it in a working condition where users can come in and submit payments through a credit card. They are then taken to a 'success' page which provides the information that they paid for. The problem is, I need to set up the webpage so that after payment is entered through Amazon Payments, my page checks for success or failure. If a successful payment is returned from the Amazon Payments reply, send the customer to my existing "Success" page. If the payment fails, it should send them to another basic webpage that says "Your payment failed". If you have set up a webpage that access Amazon Payments, most likely you have done this in the past.