Try using the poles as vertex hooks. First select one pole, then (while its still selected) go into edit mode on the plane. Press [Ctrl+H] when you have the vertices that you need to have be parented to that pole selected. Do the same for the other pole and you should be done.
That’s what will happen if you just move the poles by hand. But if you animate the motion of the poles and have the cloth simulation running at the same time, with the pinning group being exactly the two sets of vertices that are hooked to the poles, you should get the result you want.