members & lurkers

Is it possible to stop people from viewing certain forums until they have reached a certain number of posts. Can this be set up automatically or would i have to personally edit there permissions on their account.

I want to do this to encourage people to take an active part in the forum.

Any help and advice would be much appreciated.

You can make it so only certain groups can view certain sections. So maybe make groups for people with 100 posts, 500, etc.