Am I correct in my assumption that this trick will not work in Outlook
Express?

Doesn't seem to work in Agent, either. All I see for choices are
Author and Subject.

I spent an hour trying to get it to work in Agent, no joy :-(

Oops. Sorry guys. I don't use a PC and it didn't occur to me that a
basic selector like a newsgroup name wouldn't be available in your
reader's killfile setup. On the bright side, it means you'll never have
to learn how to do regex... (I'd drop the Agent people a line and ask
them to drop it in their next release. It's not exactly difficult to
implement.)

Dave.