Is there a 'user' acl?

Hi,
Sorry about the long post but wanted to include detail. I have looked at the
FAQ and nlanr site, but can't see an answer (yes or no). But then I don't
always know what I am looking for!

I have proxy authentication working using the ncsa_auth module.
I have six password files that users can update their passwords in using a
cgi script based web page.
Every 15 minutes cron cat's the files into the main one that is used by Squid.

What I would liek to be able to do is to have an acl that looks up the current
users name in one of those six files and allows access based on whether
they are in it or not. Make sense?

I tired
acl Year11 prox_auth "/etc/squid/etc/proxypwd.yr11"
http_access deny Webmail !Webmailclients !Year11
Squid accepted this when reconfigured (webmail clients is a src acl), but
whether the user was in the proxypwd.yr11 file or not the Password dialog
box continues to come up (3 times and then it tells me about having to be
authenticated).

I also tried the 'user' acl but Squid complained that this was an invalid acl
type when I reconfigured.

--
Simon Bryan                    sbryan@olmc.nsw.edu.au
Information Technology Manager sbryan@mpx.com.au
OLMC Parramatta