Camera DOF distance on Camera Frustum?

I’m wondering if theres a way to see where the DOF focal distance is at on the camera frustum. Sure I can adjust the distance until it looks like its in place, but how do I know if its truly sitting right on the focus of the camera? In Source Filmmaker you could see -exactly- where your DOF distance is sitting on the camera frustum which made it super easy to make sure your DOF was set at the perfect distance.