One solution for selling simple link product, but limited

My client's selling a simple link to an ASP form that:

1. Collects the customer's data.
2. Calls on a component to merge the data with a fillable PDF.
3. Gives the completed, merged PDF back to the customer in their browser.

It's not a download to the customer until step 3, instead it's server-side script running. Two totally different actions -- download goes to the customer's browser (and) script stays and runs on the server.

ZenCart can only handle true downloads. Lots of threads here about this deficiency in ZenCart (or any shopping cart, I couldn't find any 'cept a delivery service Modular Merchant, but it wouldn't work with the component).

So, in ZenCart, I revised define_checkout_success.php to include the ASP file link along with text instructions. This works great for one product, but it can't be used for multiple products since each one has their own different link and define_checkout_success is a blanket statement included with every successful checkout.

For multiple products with varying links, I'm now investigating whether I can have an individual define_checkout_success.php assigned to each different product.

The customer can only purchase 1 product at a time. So, it's a matter of telling ZenCart, if you sell product #8781, you're going to use define_checkout_success8781.php which would have the ASP file link for that product.

Suggestions? Ideas? :lookaroun

Oh, yeah, I used the area for Product Notification to place the instructions and file link. This site doesn't need that feature.