hi Xiaoyuli
I think what u are asking will require you to actually edit your DNS zones and whatnot.
My only suggestion if you cant get vbseo team opr forums to help you is to visit this site
http://www.gitme.net/php/ and see if url2subdomain is of any use to you.
hope you get your problem sorted!
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let me just add that google and other search engines will penalize you site for subdoamins if im correct.
Can somebody confirm this?