Multiple OWA URLs

Hi

Does anyone know if it is possible to use two separate OWA URLs in exchange 2010?

We have one exchange server used by two schools. Exchange is used at one site and uses their domain name. The other school logs on using the current URL but would like their own URL to be used.

I tried creating a CNAME that points to the owa address of the current exchange server and this fails.

Thanks in advance.

Shane