Change subfolder url to subdomain without physically moving data

I Want to Change subfolder url to subdomain without physically moving data .... using .htaccess rewrite .

like http://www.fitnessmatter.com/forum should change to http://forum.fitnessmatter.com

I dont want to move the data and also I dont want to create any subdomain .... I thnk its possible via setting up rules in .htaccess

Hello,

It is mandatory to create a sub-domain, otherwise your forum will point to nowhere.

Originally Posted by Andrés Durán Hewitt

Hello,

It is mandatory to create a sub-domain, otherwise your forum will point to nowhere.

But sir, how can vbseo do it without creating any subdomain....

I mean I have installed vbseo on http://www.dstreetdirect.com and after logging in to vbseo and changing Blog url and CMS url in "URL Rewrite Settings" to blogs.dstreetdirect.com i changes the url from Advance Tab. And I have not created any subdomain blogs.dstreetdirect.com .....
(See screenshot) ..

how does it do so without creating any subdomain ?