[maincode]

Или можно использовать библиотеку FPTween:
testRotation.swf

package
{
	import flash.display.Sprite;
	import flash.display.StageAlign;
	import flash.display.StageScaleMode;
	import flash.events.MouseEvent;
	import flash.text.TextField;
	import flash.text.TextFieldAutoSize;
	import flash.text.TextFormat;
 
	import fl.transitions.easing.Strong;
 
	import ru.flashpress.tween.anim.FPTween;
	import ru.flashpress.tween.events.FPTweenEvent;
 
	public class testRotation extends Sprite
	{
		private var tween:FPTween;
		public function testRotation()
		{
			this.stage.scaleMode = StageScaleMode.NO_SCALE;
			this.stage.align = StageAlign.TOP_LEFT;
			//
			var textField:TextField = new TextField();
			textField.autoSize = TextFieldAutoSize.LEFT;
			textField.defaultTextFormat = new TextFormat('Tahoma', 40);
			textField.text = 'FPTween lib';
			this.addChild(textField);
			textField.x = 100;
			textField.y = 100;
			//
			tween = new FPTween(textField, 'rotationY', Strong.easeOut, 1);
			tween.addEventListener(FPTweenEvent.FINISH, finishHandler);
			//
			this.stage.addEventListener(MouseEvent.CLICK, clickHandler);
		}
 
		private var rot:Number = 0;
		private function clickHandler(event:MouseEvent):void
		{
			tween.start(20, '+20');
		}
 
		private function finishHandler(event:FPTweenEvent):void
		{
			switch (event.state.animationId) {
				case '+20':
					tween.start(0, '-20');
					break;
				case '-20':
					trace('complete');
					break;
			}
		}
	}
}