Rotating and ease


I’m new to this forum and fairly new to action script.

I was wondering if anyone could give me an idea or point me to some direction in the following problem.

I’m trying to animate some leaves that rotate back and forth to simulate leaves blowing in the wind. I got to animate the leaves one way, but i couldn’t figure out how to make it loop (go back and forth).

Here’s the code:
on the movie clip named “leaf” witht the following code attached to it:

onClipEvent (load) {
_root.leaf._rotation += -15
onClipEvent (enterFrame) {
i = this._rotation;
dif_rotation = i+_root.leaf_rotation;
setProperty(this, _rotation, i-_rotation/12);

any help will be appriciated.
thanks in advance