Moving/dragging movieclips

startDrag() and stopDrag()

Only movieclip symbols can be set to be draggable.You need to use dot syntax to specify the name of the instance that will have this method applied to it.
movie_mc •startDrag();

Dragable in an area

http://www.riacodes.com/flash/draggable-area-with-as3/

area_mc.addEventListener(MouseEvent.MOUSE_DOWN, dragArea);
area_mc.addEventListener(MouseEvent.MOUSE_UP, dropArea);

function dragArea(e:MouseEvent):void{
var bounds:Rectangle = new Rectangle(
stage.stageWidth - area_mc.width,
stage.stageHeight - area_mc.height,
       area_mc.width - stage.stageWidth,
       stage.stageHeight - area_mc.height,
       area_mc.width - stage.stageWidth,
       area_mc.height - stage.stageHeight
);
area_mc.startDrag(false, bounds);
}