Need PayPal processing to trigger automated user registration

I have a WordPress-based site (www.archicadtemplate.com) which sells a downloadable product for architects (a startup kit for the ArchiCAD design software), and have maintained a separate Forum at http://www.bobrow.com/forum which uses FusionBB. I’d like to integrate these together, by implementing the Simple:Press Forum plugin for WordPress.

Here’s my challenge / question: is there a way to trigger an automatic user registration when a PayPal payment is made?

I have been manually entering people into the Forum user registration (up to this point) and want to automate this process. I’d like to make it as easy as possible for people to buy the products, so I don’t want to require that they register on the WordPress site BEFORE purchase.

Is there a plug-in that can be triggered by a PHP page on the site, and complete an “automated” user registration? When PayPal accepts a payment, it can send the person to any desired website address. If this URL actually triggers a WP plug-in to run, perhaps it could register them for the WP site as a user, then I wouldn’t have to do it manually every time someone purchases.

Once the user is registered, I will also need to add them to a “privileged” group in Simple:Press, which the developers say may be possible – but they indicated that the user must be in the WP database first, and to seek help here for that part.

If nothing exists off the shelf, I am open to paying someone to create a tool like this.

Any suggestions or volunteers??

Eric Bobrow
Los Angeles CA
eric@bobrow.com