Web Clusters

I want to put two Windows 2003 EE web servers in a DMZ to
serve a public accesible web site. The servers also need
to be accessible within our private network. We want to
use Microsoft Network Load Balancing on the web servers.
I am not 100% sure of how to do this. Do I need five IP
addresses, two private for the serves, two public for the
servers, and one public for the virtual address or do I
need only three IP's, two private for the servers and one
public for the virtual that is nat'd to the private
IP's? Please help!!

Thanks