I understand them now :-)
Apparently, the poster wants to use authentication on Squid against a LDAP server, and use LDAP groups to decide whether the user is allowed or denied.
Apparently, there is no way to do that with Squid itself. But it sounds like a simple thing to do using an external program.
Who knows, I may write it, too ;-)
Other comments showed concern about this passing cleartext passwords. That is true. Simple modifications to the scripts should prevent the POP3 or IMAP access from doing that, but I know no way to make Squid use an encrypted link for the authentication (At least not without using Squid v3).