I figured out how to Tween a curve just using ENTER_FRAME. Am I missing something in GreenSock that does this?
import flash.display.Shape;
import flash.events.Event;
var newMoon:Shape = new Shape();
var controlX:int = 30;
var controlY:int = 150;
var anchorX:int = 100;
var anchorY:int = 200;
newMoon.graphics.lineStyle(1, 0);
newMoon.graphics.moveTo(100, 100);
newMoon.graphics.curveTo(controlX, controlY, anchorX, anchorY);
addChild(newMoon);
addEventListener(Event.ENTER_FRAME, onEnterFrame);
function onEnterFrame(e:Event):void
{
controlX++;
newMoon.graphics.clear();
newMoon.graphics.lineStyle(1, 0);
newMoon.graphics.moveTo(100, 100);
newMoon.graphics.curveTo(controlX, controlY, anchorX, anchorY);
}