problem creating sub domains

[Gyroscopic]

Hi,

I have a VPS hosting solution and want to create a sub domain for one of my sites but the plesk Panel only has "Sub Domain as a new website" option not the "as sub directory" as mentioned in the documentation.

The sub domain will be linked to the original website so its not a new site. How can I set this up manualy from the console?

I would like to have something like, forum.domain.co.uk which will point to the sub folder/directory 'forum' in the site structure of domain.co.uk

I know I have to modify the apache include file for the domain but not sure exactly what I have to put or if anything else is required. Any ideas?

Thanks in advance
Gyro

---- Can someone please reply - Even if its just to say it cannot be done? Thanks!