Well yes, the END RESULT is that the horse should have forward movement, but when you are first teaching this, IMO, you should set it up for success and start from the halt to let the horse get the idea. That way the rider doesn't micromanage the horse by driving them forward if they were to start the exercise straight from the walk or trot. I don't agree with driving a horse with your seat anyway, but that's just me.
One more thing jazzyrider.......this happened with my horse, it may or may not happen with your horse. When I started combing the reins at the halt, he thought that meant back up. So IF your horse backs up, just go with her. Keep combing the reins and just be there for her, let her figure the puzzle out. And when she does, give her a BIG release. :)