Godaddy and domain masking?

I've got my website all setup and bought a domain name with godaddy. I setup the domain forwarding and masking yesterday but it doesn't seem to be masking anything.

I'm cheating and hosting my site at google. What do I need to put in godaddy's domain masking to go from this:

http://mydomain.googlepages.com/index.htm

to this:

http://www.mydomain.com/index.htm

It's a bit complex, however by setting up CNAME records, it's possible to point to your domain with full google App cabability.

http://www.google.com/support/a/bin/answer.py?hl=en-uk&answer=47283

for example, you'll have
- the googlepage you still can use
- gmail for your domain
- calender etc

Thanks very much ;)

All set up now :D Just waiting for the changes to take effect