Thanks for getting back to me. Let me try to rephrase it...
I want the customer to use the e-junkie cart for buying items from multiple suppliers. Maybe e-junkie fulfills downloads, Cafe Press fulfills shirts and another company for DVDs. In this case, e-junkie handles the transaction, but sends the order to the 3rd party(s).
I think this holds the answer: http://www.e-junkie.com/ej/help.integration.php
But, I'm not super technical, so I'm looking for verification that the above is the answer.
As a follow up... Are most web-based vendors (Cafe Press, DVDBaby, etc.) set up to receive and process the variables and/or the "Payment Variable Information URL"?