mod_rewrite and subdomains

[Stoned Phillips]

Dunno if this is the right forum for this post, but I need some help.

I'm offering a free website, and the users URL will be http://www.mydomain.com/user , is there a way using mod_rewrite to make it http://user.mydomain.com , without actually having to create the subdomain? I would also need it set up for their subdirectories, like http://user.mydomain.com/sub/sub

I've been looking for the answer, but no such luck. Hope ya got an answer for me.

TIA