Moving to Usergroup via Selection

[bonjurkes]

Hello,

I saw a hack for moving users to proper usergroup via selection at registration..

Something like :

At user registration part there will be question like "do you want to see adult content" if user choose no, it will move to usergroup that cant see adult content (i will create a usergroup that cant view these forums via access mask) and if user choose yes it will register as normally

Is there a hack like that??