How to disable members to send PM`s?

I want every member to post 7 posts before they are allowed to send PM`s,how do i do that?Thanks in advance

First you go to the member's profile, then scroll down at the bottom
it'll say Can send PM's? or something like that, you just fill click in "no"
It might take a long time though if your forum has a lot of members

that can only be controled by disabling/re-enabling each members PM personally.
to do so
remove PM box
Admin panel>>user & Groups >> select user and go into admin panel profile >> scroll down to bottom of page and find "Can send Private Messages :" Option 2 (No) >> save
and than do the same but make "yes" instead of "no" to re-enable the PM box
Sorry if this is complicated

Thanks for answers ,so then its not possible to do this in just one move then....