[Help] Creating an activation page for paying customers

Hi,

I have an application I'm trying to sell on my site. The way it works is that a client will install the app on their site, once on their site, it will generate a uniquechallenge code then they will send me that challenge code I will respond with a license key then they will use that to activate the application on that site only. If they want to install it on another site or many, they need to send me challenge code for each site.

Given this, I'm trying to figure out the payment workflow. So if someone comes to my site, www.spdash.com and purchase 5 licenses, they then need to email me with 5 challenge codes, I need to generate the licenses and email them to the client.

I'm wondering if I could automate this somehow by giving the paying user access to the activation page by emailing them a link after purchase, but in this activation page, it would know who the customer is and how many licenses they are allowed to activate. So if they purchases 5 licenses, they can only generate 5.