Game code issue - as3 newbe

I want to move these boxes around the screen independantly. For level 4 I get stuck in what I dont no. The boxes also seem to move as a unit too.

I feel like there is a more simple way to do what I want here too. Go easy one me this is my first attmpt at simple gaming code.

Link to the swf - Get to level 4 and you will see the issue.
http://www.wisc-online.com/prototypes/Jgame/shooter.swf

Full source files
http://www.wisc-online.com/prototypes/Jgame/shooter.zip

Heres an image of what I want to happen.
http://www.wisc-online.com/prototypes/Jgame/image.jpg

Code:

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var Dir:String = "down"
var Speed:Number = new Number()
addEventListener(Event.ENTER_FRAME,myFunction);
function myFunction(event:Event) {
        if(CurLevel == 1){
                //Do not move boxes
        }else if(CurLevel == 2 && CanPlay =="yes"){
                Movelevel2("mc0");
                Movelevel2("mc1");
                Movelevel2("mc2");
                Movelevel2("mc3");
        }else if(CurLevel == 3 && CanPlay =="yes"){
                Movelevel3("mc0");
                Movelevel3("mc1");
                Movelevel3("mc2");
                Movelevel3("mc3");
        }else if(CurLevel == 4 && CanPlay =="yes"){
                Movelevel4("mc0");
                Movelevel4("mc1");
                Movelevel4("mc2");
                Movelevel4("mc3");
        }
}


function Movelevel4(mc:String) {

        for (i=0; i<4; i++) {
                if(this[mc].x>720){
                        Dir = "downleft"
                }else if(this[mc].x<-50){
                        Dir = " upright"
                }else if(this[mc].y>500){
                        Dir = "upleft"
                }else if(this[mc].y<150){
                        Dir = " downright"
                }
        }
        if(Dir == "downright"){
                for (i=0; i<4; i++) {
                        this[mc].x+=Math.ceil(Math.random()*3);
                        this[mc].y+=Math.ceil(Math.random()*3);
                }
        }else if(Dir == "upright"){
                for (i=0; i<4; i++) {
                        this[mc].x+=Math.ceil(Math.random()*3);
                        this[mc].y-=Math.ceil(Math.random()*3);
                }
        }else if(Dir == "downleft"){
                for (i=0; i<4; i++) {
                        this[mc].x-=Math.ceil(Math.random()*3);
                        this[mc].y+=Math.ceil(Math.random()*3);
                }
        }else if(Dir == "upleft"){
                for (i=0; i<4; i++) {
                        this[mc].x-=Math.ceil(Math.random()*3);
                        this[mc].y-=Math.ceil(Math.random()*3);
                }
        }else if(Dir == "down"){
                for (i=0; i<4; i++) {
                        this[mc].x+=Math.ceil(Math.random()*3);
                        this[mc].y+=Math.ceil(Math.random()*3);
                }
        }
        }

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