Amount of days to post link

I want to know how I can add something that calculates the amount of day you have to be registered to add a link to your forum so does anyone know how to add cause if you do I would really be happy if you can tell me how

Are you asking for restricting your members from POSTING, or restricting them from including their forum link in their profile?

I only want it for posting

It will be at ACP > General > Security > Tick "Yes" for "Unauthorize members with less than a week registration to post external links and emails"

Cheers