Problem with multiple source and destination groups

[b1rdy]

Hi all,
Firstly, apologies if this is a dumb question but after the week I've
had I'm having problems understanding how a toaster works.
Basically, what I'm trying to achieve is a config with multiple source
and destination groups, and I can't get it working.  From reading all
the documentation I'm beginning to suspect that what I want to do is not
possible.
So, here's the scenario...
I want to be able to use multiple block lists, such as porn, gambling,
etc, and then specify which users will be blocked by these individual
lists.  Example:
user1, user2, user3 to be blocked for porn sites.
user2, user3 to be blocked for gambling sites.
The problem as I see it is that a user cannot be a member of more than
one source group.  If user2, for example tries to access a gambling
site, he's first seen as being part of the porn group and since the
gambling site he's trying to access is not part of the porn blacklist,
he's allowed to pass.  If he tries to access a porn site, he's blocked
fine.  Am I understanding this correctly, or is there a way around it?
I have included my current config below.

TIA

Mark Read


Current squidGuard.conf:

logdir /usr/local/squidGuard/log
dbhome /usr/local/squidGuard/db

src porn-group {
        user    user1
        user    user2
        user    user3
}

src gambling-group {
        user    user2
        user    user3
}

dest porn-list {
        domainlist      porn-domain-blacklist
        urllist         porn-url-blacklist
}

dest gambling-list {
        domainlist      gambling-domain-blacklist
        urllist         gambling-url-blacklist
}

acl {
        porn-group {
                pass !porn-list
        }

        gambling-group {
                pass !gambling-list
        }

        default {
                pass all
                redirect http://www.google.com
        }
}