I dont think I get what your saying here... you could do Members only (hidden) forum and then select the members from the list that you want to be able to post there.
You could allow moderation for that category/forum, then enable moderation for that forum, that way everybody could read topics, but in order to post a topic it would first have to be approved by and administrator/moderator.
Ok! But in that way I have to monitor it 24h a day *S* I have made a new accesstype called "Read only - memberlist can write", and it works like I wan't it to...