Car Seats

I've heard before that it's possible to have a top tether point installed into a car that's missing one - is this true? As it stands, my 08 Town and Country van only has 3 - one for each captains chair in the middle row, and just one for the 3rd row seats in the middle position. (only place with LATCH connectors too) I'd really like to move both of my big kiddos (4 & 2, in FF Nautilus and a Marathon) to the third row when the baby comes. Baby will be in an infant seat in the passenger side captains chair, and I want to stow the other captains chair under the floor for easy access to the back row seats. However, I'm not comfortable having one of the kids seats in the back not tethered - so can I have this situation remedied? Am I missing an anchor point? I don't have the manual on this vehicle, b/c we bought it used a few months ago.

Thanks!
Rebecca

Why is that? Not that I don't believe you, I'd just like to know what the rationale is?

Thanks!