Add local intranet site and automatically detect intranet network enabled via GPO

I have a mix of IE7 and IE8 machines that I need to add a specific URL into the "local intranet" zone, then also make sure that the "automatically detect intranet network" option is enabled.  I need to at least get the URL added into the local intranet zone, as i think that other option may be enabled by default or might also be unnecessary if the URL to our intranet is added specifically as part of my first request.  How can I do this via a group policy?