Create UserName, Send to Database

Hi, I'd like a script that, in SUMMARY, does the following: *** Automatically makes the buyer of an ebook from SalesWebsite01 a member of a forum hosted at ForumWebsite02. *** In OUTLINE, this script: 1)Invites a customer to submit a username and email address; 2)Creates a password that attaches to that username and email address; 3)Reveals that password to the customer; 4)Writes that username/password/email address combination into the userlist for a forum attached to a different website (and, if necessary, hosted by a different company). 4)Result: Customer can now enter enter forum contained on a different site. And in finer DETAIL: 1) User purchases an ebook via Clickbank, PayPal, or 1shoppingcart/Linkpoint from SalesWebsite01. 2) On download page, OR, alternately, via link contained in "Thank You" email, customer is given place to enter username/email address. Note that username must not conflict with usernames already in system at ForumWebsite02. ***Note that visits to the download page are being tracked for conversion purposes, and will already carry scripts and tokens. Unless you can find a way to incorporate these elements, dynamic pages must be avoided in favor of static html/php pages. 3) Different usergroups at the forum have access to different forums. 4) Different purchases from SalesWebsite01 (or indeed, SalesWebsite02 or SalesWebsite03-- different sites will feed into the forum site)-- will put customers into different usergroups. Presumably a parameter must be given a value by the script and then sent by the script that tracks which product the customer bought, and therefore which forum usergroup the customer will go into. 5) In any case, customer must somehow get all the info needed to login at ForumWebsite02's secured forum. ***Note that I WELCOME your suggestions on the best way to structure and sequence this process. You can probably come up with a more-efficient approach than the one I've outlined, or at least a smart, lightweight way of doing this, and again, I welcome your suggestions.*** If you can install, that would be great also. Thanks!