Redirect using ENV VAR

[TimL]

I would like to have a script I can place in my html page that when a user opens the page it will check the users REMOTE_HOST and
or REMOTE_ADDR and determine if the first six digits of their isp is 123.456 if it is it will then redirect them to a specific URL and page. If it isn't then it will open the html page.

Can someone show how this should be written?

Thank You.

[TimL]

Dave,

Thank you for your reply. I will give
this a try. My host does support SSI and
I will add the extension shtm.

TimL