How to generate random Registration Codes after purchase

Hi Everyone,

I’m looking for a plugin that could generate a random, unique registration code on my blog when beeing called by a paysite like paypal, minipay etc.

Here’s what I’m trying to do:

I run a blog where members can sign on for an annual membership. They pay amount XY and get a registration code so they can register for my – private – blog.

So far I plan to use the plugins wpinvite and Registered Users Only 2 to do the job on limiting / managing access to my site.

Payment shall be done through german service minipay – they have a wp plugin .

Only Problem is generating new registration codes whenever a customer comes back from minipay. Maybe something like a code generator – the landing page after checkout from minipay would show a dialog like: “Thanks for supporting XY. Generate your Registration Code now”. Alltogether the process should be:

1. User comes back to landing page after purchase (point of sale is not important, could be minipay, could be paypal etc.)
2. A Dialog / Form: Enter your Mailadress (or maybe this could be taken from data of purchase? :-))
3. Generate your Registration Code
4. User strikes “Generate”: Unique, E-Mail Bound RegCode is generated and stored to database
5. WP sends Mail with registration code to user for future reference

Anyone with an idea? 🙂 Thanks a lot!