usergroup by domain on registration

[Valter]

Hi all,

Here is what I need:

1 server
1 vB instalation
2 domains

When user comes from domain1.com and register he automatically goes to usergroup1.

When user comes from domain2.com and register he automatically becomes member of usergroup2.

Then i will set different permissions for those usergroups.

Is it hard to do this? And is it ok with vB rules to use one forum with two domains?

Any help is really appreciated.