Convert Gaphics into Move Clip

Question

Here, I am create three files. Box.as for making graphich dimentional box, Drag.as is for dragging movieClip and ShowBox.as is to display draggalbe box. I would like to see box with draggable faclity. But I am getting error followig error.
Description : 1067:Implicit coercion of a value of type Box to an unrelated type flash.display:MovieClip  on Show Box
Might be I am getting problem of converting into move clip but I am not sure. Would u mind u you gind me in this problem/
Box.as
package {
     import flash.geom.*;
    import flash.display.Shape;
     import flash.display.Sprite;
     public class Box extends Sprite {
          public var box:Shape;
          public var boxWidth:Number;
          public var boxHeight:Number;
          public var boxColor:Number;
          public var boxBorderSize:Number;
          public var boxBorderColor:Number;
          public function Box() {
               //Assign Value
               boxHeight=100;
               boxWidth=100;
               boxColor=0x000000;
               boxBorderSize=1;
               boxBorderColor=0xCCCCCC;
               box=new Shape();
               box.graphics.lineStyle(boxBorderSize,boxBorderColor);
               box.graphics.beginFill(boxColor);
               box.graphics.drawRect(0,0,boxWidth,boxHeight);
               this.addChild(box);
Drag.as
package{
    import flash.events.*;
    import flash.display.Sprite;
    import flash.display.MovieClip;
    public class Drag extends Sprite
        public var clip:MovieClip;
        function dragBox(myClip:MovieClip)
                clip=myClip;
                clip=new MovieClip();
                clip.addEventListener(MouseEvent.MOUSE_DOWN,startMyDrag);
                clip.addEventListener(MouseEvent.MOUSE_UP,stopMyDrag);
                addChild(clip);
                function startMyDrag(evnt:MouseEvent)
                    clip.startDrag();
                function stopMyDrag(evnt:MouseEvent)
                    clip.stopDrag();
ShowBox.as
package{
     import flash.display.Sprite;
     public class ShowBox extends Sprite
          public var myMask:Box;
          public function ShowBox()
                myMask=new Box();    
               myMask.boxHeight=100;
               myMask.boxWidth=100;
               myMask.boxColor=0x000000;
               myMask.boxBorderSize=1;
               myMask.boxBorderColor=0xCCCCCC;
               addChild(myMask);
               var myDrag:Drag=new Drag();
               myDrag.dragBox(myMask);
               addChild(myDrag);

Answer 1

I do not understand. Acutally, I want to drag the box . Thus, I want to make it movie clip throug AS. I have made graphic rectangular but could not convert nto movi clip. Is there any function so that I could change my graphic into movie clip .