How to make them post

[sponsorchat]

My forum gets a lot of new members, I have a lot of lurkers, like hundreds at a time, I made it so only logged in members can read posts, still doesn't work.

What I'm trying to do is make it so if a member logs in say 50 times and doesn't post he'll get a message that unless he participates by posting he'll get banned.

Is there a way to do this?

It's not a library, it's an interactive place, if everyone keeps reeading eventually there won't be anything to read, we need posts.

Thanks