i need help with new user on new directory on subdomain

ok lets be brief. i need solution for new register user to automaticlu get adress like : http://www.blog.mydomain.com/newuser ( so every new user to get new directory and adress )
i simply read faq and forum here but i cant find answer for this . So if any one can help me lets write here pls.

ty

curently i made deirecotry my self via ftp ( i go to subdomain made deiretory and again instal world press but this take a lots of time and space. I do this for on this link http://www.blog.vlasotince.com/bamby – so pls help if any one know hot to make this automaticly 1

i start blog again world press on http://www.blog.vlasotince.com so if this can help someone lets try to register or whatever