I assume there is a way with mograph but I dont know it.
I think I would use 2 planes and then a bend deformer on each one. Or maybe a single plane with a bend deformer in a symmetry object.
You can use PLA (point level animation) first you need to enable PLA. there is a botton under the time line with a bunch of dots on it in a group with move, scale, rotation make sure its highlighted too (its off by default). Then in Point mode you can key frame your points position. I generally use it with a morph deformer but that goes with mocca.
/Randy