Originally posted by: embj
What you'll need to do is go into the IIS manager and go to the companyweb properties. Then, right beside the IP address, click the advanced button. Now, you'll need to hit add under the multiple identities for this website. Then just fill in the IP address, the port, and the host header (you should set it to "companyweb.yourdomain.com" -- without the quotes). Then, just setup a DNS record to point to your subdomain. That should do it for you.
EDIT: I just noticed in the topic name you said it was SBS....so all that you'll really have to do is setup a DNS record to point to companyweb.yourdomain.com.