Inside or outside the firewall.

Hi,
Is there a way to determine if a user is connecting to a website from inside or outside a firewall?
Right now I'm simply comparing the server variable REMOTE_ADDR to a list of IPs for our internal computers but this needs continual maintanance.
Thanks,
Al.

If the firewall is good there shouldn't be a way of knowing they are using a firewall.

Hi,
Maybe the firewall isn't what I mean.
Is there a way to tell if a user is connecting to the site by way of our intranet as opposed to the internet?
Thanks,
Al.