[Typo3] subdomain plus domain on same installation

[Christoph Koehler]

Hey there,

I would like to add a new site as a subdomain, totally disconnected from  
the main site on the main domain. So I would like the subdomain address to  
stay in the URL field. But I would like to be able to use my existing  
TYPO3 installation instead of making a new one on the same host.

I tried redirection to the main site from cpanel and use domain records,  
but then the address field changes to the main domain, as well.

This seemed so easy and logical, but I cannot figure it out...

Thanks for the help!

Christoph