Unfortunately I don't think Outlook provides that feature.
Not sure if it's an option for you, but I use a dedicated newsgroup
provider
(newsguy.com), and they support NNTP (Outlook, Agent, Xnews, etc.) and Web
access to the newsgroups. Their service costs me about $3/month and they
include
5 email accounts and web space along with newsgroup access.
Their Web interface has a built in newsgroup search engine, automatically
decodes multi-part binary posts (video, mp3, etc.) and they have a
reply-trac
feature that does what you've described.
You can basically flag a specific message, a discussion thread or an
entire
newsgroup and their Web interface will notify you through email or the Web
when
any posting activity occurs. It's a convenient way to stay current in your
favorite newsgroups without having to stay connected to the groups 24/7
It takes a little getting use to, but I've found myself using my NNTP
reader
less (Xnews) and their Web interface more frequently because it offers
handy
features my NNTP reader doesn't offer.
vin