Hittesting movieclip with movement inside it

In short, I’m making a game where your character must touch rings (big ovals) that are moving up and down with a motion tween (with easing). I attach these movies and push them into an array. For the hittesting, nothing is accurate. Since a movieclip inside the ring movieclip is moving up and down, the boundary box is much bigger than it should be when hittesting. If I use the x/y method, it triggers the hittest when my character is in line with the reference point. It should trigger when the middle of the character hits around the middle of the ring. How could I do this?

Thanks.