Gradient tween

I want to make an effect, with a motion tween. I have a shape with a gradient fill in the first frame, in the 25-th I changed the gradient direction and made a motion tween hoping to see how it slowly changes, but noting happened. How to make this effect???
Flash CS3, AS 3.

I know this is an old post but I just thought I’d answer this question in case anyone else stumbles across it.

You can do this with a shape tween (not motion tween).