[Request] Having to approve first post of a user until further posting

[Kikkerking]

Alright, this might be a little hard but I dunno, I'll just request it as I quite need it. What I want is, that if a new user signs up and posts at my board, I (admin) has to approve the first post they make before they can post anymore. That is a great way to determin if a user is going to be a spammer or not. I'd also like an option that makes an admin able to choose how many posts of a new user would need approval. Thanks in advance!