Virtual Directories in IIS6.0

im running a Network what has a internal network which is the green network, a DMZ where my external web server is, which is my orange zone and typically a red zone which is the internet.

I want to create a virtual directory to be published on the web server which is not part of the internal domain. I want the virtual directory to be pointed to a shared folder on the internal network.

I only want valid domain users to be able to access the virtual directory.

Any links to other pages or tips would be great.