Barclays Payment onto FLASH website

I have a website which will be finished this week. Upon checkout, the buyer chooses PayPal, cheque or Credit Card. At the moment, the credit card function is programmed to go to Protx, as that is all the writers know how to do. I need the checkout to go directly to Barclays and not Protx. I need someone who has done this before, as I understand it is a small job but obviously it is important it is done correctly. I don't have much more info... I am still awaiting acceptance for the Barclays merchant account... should hear next week. They supply some sort of URL (i don't know the technical details) and it needs to be plugged into my site. My site is written in flash so I need a flash expert. Any questions, please ask!