New Registrations to Different Usergroup via Link or referrerid

[pmdpmd]

Hi,
I would like to assign new users that arrive via a specific URL to a different usergroup than "Registered Users".

For example, I could publish the link as "www.website.com/register2.php" and I could put a copy of register.php at register2.php with the appropriate mods?

What I am trying to achieve is to allow only the members of a local club to have access to a private forum for them. I have set up the new forum and a new usergroup and ensured that only members of that usergroup can access the forum.

Now I want to send a mail out to the members of the club with a URL for them to click on to register at my site after which they will have automatic access to that private forum.

I would welcome suggestions on how best to achieve this.

Thanks,
Paul.