UBB.threads PHP Forum Software Community Forums Resources and Customizing How Do I? prevent new user from posting in our sales board unless they have posted 10 times on other boards

Hi

It seems that we have scammers login in on our forum. They publish a stolen image of a motorcycle and offer it cheap.

my moderator of our sales board asks if I can set up a rule that prevent new user from posting in our sales board unless they for example have posted 10 times on other boards.

I understand what he is after but have no clue how to arrange for this to happen. Do you guys follow what i'm saying? and if solo you have any idea on the subject. sort of making it harder to scam on our forum.
Thanks