Lock the car from the liftgate

My CMax has door lock buttons on the front door handles.  When I pop the liftgate and get my items, i cannot lock the car here.  You have to go back to the front doors, or pull out the key fob.  (defeating the brilliant convenience of the foot sensor.)  I would love to have another lock button on the liftgate.  Alternatively, without adding new hardware, allow the lock buttons to function even when the liftgate is Open.  So i can lock the car after getting out, then close the gate and have it self lock.