I want to allow my users to list items for sale for free for a limited time offer. I successfully created a 100% discount in my ecart object so my total always equals 0. However, the next step to complete the transaction would be to go to paypal and enter credit card. This would activate the IPN which changes the value of the product to "1" in order to put the item up for sale on the listings. Basically a user pays me a $1 to list their product but I want to them to be able to list for free. How can I get my IPN to activate without sending to paypal?