domain mapping and cpanel

This is my setup:

I have a multisite installation lets call it

I have a blog on that site

I have a cPanel installation of so that I can have email accounts for

How do I map to

The domain mapping feature works fine, but it points to the cPanel hosted site of

What changes in the cPanel of do I have to make to ensure only the web traffic goes to the multisite installation.

Both of these are on the same IP address.