This post explains our overall development strategy, if you're curious:
Subscriptions for our own service just use PayPal's own Recurring Payments solution, bone stock and as-is. Our only involvement is providing PayPal's subscription buttons in the "Start/Update Paid Subscription" screen of our Seller Admin. Clicking the Subscribe button for your chosen plan level just sends you to PayPal's site, where you'd log into your PayPal account, choose a funding source, and approve the payment terms we'd encoded into the button you'd clicked.
This sets up an automatically-recurring payment schedule in your own PayPal account, instructing PayPal to just blindly send us the same amount every month with a reference to your E-junkie account ID. Separately from the payment itself, PayPal also sends an IPN to the URL of a very simple script we have which merely receives the IPN, finds an E-junkie account ID in it, and bumps that account's expiration date back by another month.
I'm sure you can appreciate that it's one thing for us to have that very simple, ad-hoc system that relies on PayPal for the actual subscription setup and payment management, where our end just does just one simple thing: changes an expiration date in our purpose-built account system, vs. quite another thing to have a flexible subscription/membership management system that is capable of handling the wide variety of things that a wide variety of merchants might commonly want to do with recurring payments.
Since you can already set up recurring payments using PayPal alone and use their IPN to notify your own system of those payments, and we currently have nothing at all useful featurewise that we could add to that, we'd rather be honest and say we have no way to support recurring payments rather than proposing a halfway solution that's no solution at all. Also, you should really only be using E-junkie's Transaction Log as a record of orders that you have used E-junkie to accept and fulfill; for accurate and complete financial recordkeeping and reporting, you should really be using your account history with PayPal.
That said, here's something you MIGHT be able to get working:
You would need to use PayPal's own recurring payments button code to take the initial order on your site and set up an auto-recurring payment schedule in the buyer's PayPal account.
You would also need to manually configure your PayPal IPN settings according to those given in our eBay integration instructions:
When we receive an IPN from PayPal, our system matches the payment recipient's email with your E-junkie account's PayPal Email setting, then it would attempt to match the Item Name given in the IPN with the Item Name of a product in your E-junkie account. Our system should then process the order as usual for that product (e.g., if it has a file download, we'd issue the buyer a link for that file).
Bear in mind this use of our system would be considered an "unsupported hack", so we may not be able to provide any further advice or assistance in setting this up and getting it to work or troubleshooting any problems you may encounter. We're not even sure what I've described above will even work at all, since it's never actually been done before, so at this point we can only say in theory that it might work.
"In theory, there's no difference between theory and practice, but in practice, there is."
-Jan L.A. van de Snepscheut