How to hold members to viewing profiles until 15 posts?

[Ckidd25]

I created a usergroup, called "New Members" and I don't want them to be able to access user profile fields (prevents spam), and once they reach 15 posts, it enables them to change usergroups and view it.

How do I do this?

[Dismounted]

<a href="http://www.vbulletin.com/docs/html/main/usergroup_promotions" target="_blank">Usergroup Promotions</a>