My b2evolution Version: Not Entered

Hi,

I'm trying to allow users to set up a new blog, but in doing that I would like them to be able to setup their own URL Name. How would I be able to get them to do this, while at the same time maintaining the other permissions levels to make sure they don't get access to other admin areas?

In other words, is there a way to modify what each level of permission gives access to? Maybe in the coding (which functions/class should I be looking at?)