VB2 - must be registered to read threads in forum?

[Meza]

I'd like people to be asked to register when they try to read a thread in a certain forum on my site.

I have set in the forum permissions for unregistered/not-logged-in as "can view forum = no", which sort of works. If someone follows a link to a thread in that forum from another website they get an error message saying log in or sign up - which is great. But the downside is that if you're not logged in that forum disappears from view on the forum mainpage.

How can I still have the forum visible to guest, and have them see the list of messages, number. of replies etc - but just get the no permission message when they try to read a thread.

help! thanks