Originally posted by rick
Let me see if I understand.

You want to put product A on site A.
You want to put product B on site B.
You want to put product C on site C.

You want the 'checkout' to be on site D.
You want the information kept on site D.
You want the payment transaction to be on site D.

Correct?
Nope.

Product A on Domain A
Product B on Domain B
Product C on Domain C

All of them have their own 'checkout' although in reality it should just be a simple order form that passes the individual produt info a well as payment info to the processor.

Once a sale has been made on any of the domain / produts then that info is passed back to Domain C and stored.

Regards,

Lee