Simple NT Script - HELP

I was wanting to come up with a (hopefully) simple script to get the full url of the location that a person was at before they came to my site. (ie the page that the link was placed)

I realize you have to use the ENV VAR HTTP_REFFERER, but how!!??

and then I want to load a page from a file, with the URL at the top. For example:

        Thanks for visiting my page, you came from
            http://www.somewhere.com/link.html

thanks