Change path for Site Address

I am working with a government dmz that doesn't have access to the main server, so I need to change path for the site address.  It is currently trying to load from 'http://<server>/Geocortex/Essentials/Web/viewer.aspx?Site' and I want to change it to load from ' (http://www.xxxx.com/output/) http://www.xxxx.com/output/ Geocortex/Essentials/Web/viewer.aspx?Site'   Thanks (http://dc2/Geocortex/Essentials/Web/viewer.aspx?Site)