Instead of using the mouse position as reference to draw your curve, you can use a custom Point
object with the coordinates from where you want the curve to start from.
moveTo(myPoint.x, myPoint.y);
You can create any Point
you want, for example at (50,200) using the relative coordinates from your Sprite
, and then find the global coordinates using localToGlobal
.
var globalPoint:Point = mySprite.localToGlobal(new Point(50,200));
trace(globalPoint.x,globalPoint.y);