Thanks for your prompt response. I think I'm missing something though. I edited the first product ("Admission ticket- individual"), and checked "Send payment data to your server". On the next screen, I entered the payment variable information URL.
My understanding, per your help screen: http://www.e-junkie.com/ej/help.integration.php is that the transaction data will be sent to our URL via HTTP POST. To test that, I clicked on the "send free download link" option on the Seller Admin Page. Then, with the "Admission ticket-individual" item selected, I check only "Generate download link and code" and click Submit. That generates only the following text: "Admission ticket-individual".
I'm guessing that the "Generate download link and code" only works if the item being sold is flagged as a download, correct? So how do I generate a HTTP POST of some test transaction data to our server?