URL re-write when user registration

I am looking for a new field during the registration -> PHP Fox installed at: [login to view URL] The URL field will dynamically check if it's already taken. ex: Newfield: johndoe If it's not taken allow the registration. Ex: [login to view URL] Ex2: janedoe is registering she would have [login to view URL] I want to make sure I can write my own stuff that is outside phpfox in the directory: [login to view URL] and [login to view URL] It's very important that PHP Fox Content is at [login to view URL](newfield)/(wall) for every user. Once again I will save something not related with PHP Fox under [login to view URL](newfield) - While creating the directory (newfiled) copy [login to view URL] that will be provided. We are using Social Connect - [login to view URL] -> If someone is using social connect to register simply ask for the (newfield) on the first run and create the directory accordingly. The directory name can only be letters and numbers (no space or special characters). Please let me know if you need more explanation. Thank you and Good Luck.