Proxying restricted by URL *and* username?

Can I do this with Apache's proxy/access/rewrite features?

I want to set up a proxy server which users must enter a username and
password to be able to proxy to the outside world: So far that looks
pretty straight forward with mod_access and "Require user".

I want to be able to restrict proxying to allow access to a specified
list of websites: I've found a method for doing that using a text list
of websites and mod_rewrite which looks like it should work.

The problem: I want some authenticated usernames (the adults) to be able
to access any Internet site via the proxy, but I want other usernames
(the kids) only to be able to access sites on the specified list. Can I
do that? How?

I don't want to set up two different proxies, e.g. in different virtual
hosts.

(Apache 2.0, if that makes a difference.)

Thanks
Andrew

Andrew Instone-Cowie wrote:
> but I want other usernames
> (the kids) only to be able to access sites on the specified list.

May be prefix all user names for the kids with a 'k_' or something
similar. Or perform a RewriteMap lookup for the user name to determine
if it's an adult or a kid. Of course, you must keep a separate database
(e.g. txt-file) for that.

Just an idea...

--
Robert