Pulling up instructions for authentication

If I understand the sequence of events correctly, Squid works something
like this:
...
1) Squid receives a request for a url from a browser
2) Squid's acl config hits the url as one that requires authentication
3) Squid sends out the http code to bring up the dialog box in the browser
4) Squid authenticates
5) Squid gets the url
...

Is it possible to get Squid to somehow send out an html doc just after step
2, containing instructions on what to type into the dialog box that just
appeared on your screen in step 3?

Once you've been authenticated, the instructions page would be replaced by
the contents of the url you requested.

Sorry, we're Norwegian...

--
Espen Lyngaas, IT Consultant, Color Group ASA
Espen.Lyngaas@colorline.no Espen.Lyngaas@c2i.net
http://www.team17.com/~elyngaas/
Phone: +47-95063143 +47-22944315 ICQ: 43241796