Private Message Manager - usergroup setting

[TIStaff]

Is there a mod, or is it possible to create a mod that would allow more control over the PM privileges for each usergroup?

Basically what I was after was a way to restrict/control a members pm privileges via usergroup priv's. For instance, if a member is in a "restricted" usergroup they would only be able to send and receive pm's from the administrators, supermods, mods.