NEWBIE CGI HELP::Can I verify a user has logged on

From: joe slash blow (joeblow_at_nospam.com)
Date: 08/30/04 

Date: Mon, 30 Aug 2004 18:24:17 GMT

I have very basic Perl knowledge and inherited a script for work.
If the user inputs a specific 4 character code in one of 3 places on a web
page, I have to verify that the user has logged onto an NT domain account
before I let them go to the next html page. If they don't use the 4
character code they can go on unchecked.
I don't want them to have to log on to the perl page, just verify that they
are logged onto the system.
Any help would be greatly appreciated.

T:I:A!
- D a r y l