ISA 2006 in DMZ and SSL Authentication

Hello can anyone give some insight as to how this can be accomplished? Here's some setup info...

ISA 2006 Front End Firewall

DMZ - Web Proxy's - DMZ

ISA 2004 Back End Firewall

The front end firewall obviously has no connection to the domain, while the back end firewall does. I have a website that is published on the Front End Firewall, which then forwards the requests to my web proxy, which then forwards the request to the back end firewall, and then on to the actual web application. I need to add security to this setup by use of SSL Authentication. Any suggestions?

Thanks,