Some Error

/*Getting Can't Access property or Method of null object @

function aussieMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}//endaussieMouseOut
*/
import flash.media.Sound;
stop();
var soundClip:Sound;
function init():void {
    soundClip = new Sound();
    soundClip.load(new URLRequest(".\\Wheel of Fortune.mp3"));
    soundClip.addEventListener(Event.COMPLETE,soundLoaded);
}//end init()

init();

function soundLoaded(e:Event):void {
    soundClip.play();
}//end soundLoaded

txtWheel.text = "";
this.aussie_btn.addEventListener(MouseEvent.MOUSE_OVER,aussieMouseOver);
this.aussie_btn.addEventListener(MouseEvent.MOUSE_OUT,aussieMouseOut);
this.aussie_btn.addEventListener(MouseEvent.CLICK,aussieClick);

this.bigMoney_btn.addEventListener(MouseEvent.MOUSE_OVER,moneyMouseOver);
this.bigMoney_btn.addEventListener(MouseEvent.MOUSE_OUT,moneyMouseOut);
this.bigMoney_btn.addEventListener(MouseEvent.CLICK,moneyClick);

this.finland_btn.addEventListener(MouseEvent.MOUSE_OVER,finlandMouseOver);
this.finland_btn.addEventListener(MouseEvent.MOUSE_OUT,finlandMouseOut);
this.finland_btn.addEventListener(MouseEvent.CLICK,finlandClick);

this.gameboy_btn.addEventListener(MouseEvent.MOUSE_OVER,gameboyMouseOver);
this.gameboy_btn.addEventListener(MouseEvent.MOUSE_OUT,gameboyMouseOut);
this.gameboy_btn.addEventListener(MouseEvent.CLICK,gameboyClick);

this.nes_btn.addEventListener(MouseEvent.MOUSE_OVER,nesMouseOver);
this.nes_btn.addEventListener(MouseEvent.MOUSE_OUT,nesMouseOut);
this.nes_btn.addEventListener(MouseEvent.CLICK,nesClick);

this.phillipine_btn.addEventListener(MouseEvent.MOUSE_OVER,phillipneMouseOver);
this.phillipine_btn.addEventListener(MouseEvent.MOUSE_OUT,phillipneMouseOut);
this.phillipine_btn.addEventListener(MouseEvent.CLICK,phillipneClick);

this.french_btn.addEventListener(MouseEvent.MOUSE_OVER,frenchMouseOver);
this.french_btn.addEventListener(MouseEvent.MOUSE_OUT,frenchMouseOut);
this.french_btn.addEventListener(MouseEvent.CLICK,frenchClick);

this.turnTable_btn.addEventListener(MouseEvent.MOUSE_OVER,turntableMouseOver);
this.turnTable_btn.addEventListener(MouseEvent.MOUSE_OUT,turntableMouseOut);
this.turnTable_btn.addEventListener(MouseEvent.CLICK,turntableClick);

this.uk_btn.addEventListener(MouseEvent.MOUSE_OVER,ukMouseOver);
this.uk_btn.addEventListener(MouseEvent.MOUSE_OUT,ukMouseOut);
this.uk_btn.addEventListener(MouseEvent.CLICK,ukClick);

function aussieMouseOver(e:MouseEvent):void {
    txtWheel.text = "Aussie Wheel";
}//end aussieMouseOver

function aussieMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}//endaussieMouseOut

function aussieClick(e:MouseEvent):void {
    gotoAndStop("mnu_Aussie");
}//endAussieClick

function moneyMouseOver(e:MouseEvent):void {
    txtWheel.text = "Big Money Wheel";
}//end moneyMouseOver

function moneyMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}//end moneyMouseOut

function moneyClick(e:MouseEvent):void {
    gotoAndStop("mnu_BigMoney");
}//end moneyClick

function finlandMouseOver(e:MouseEvent):void {
    txtWheel.text = "Finnish Wheel";
}//endfinlandMouseOver

function finlandMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}//end finlandMouseOut

function finlandClick(e:MouseEvent):void {
    gotoAndStop("mnu_Finnish");
}

function gameboyMouseOver(e:MouseEvent):void {
    txtWheel.text = "Gameboy Wheel";
}

function gameboyMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}

function gameboyClick(e:MouseEvent):void {
    gotoAndStop("mnu_Gameboy");
}

function nesMouseOver(e:MouseEvent):void {
    txtWheel.text = "NES Wheel";
}
function nesMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}

function nesClick (e:MouseEvent):void {
    gotoAndStop("mnu_NES");
}

function phillipneMouseOver(e:MouseEvent):void {
    txtWheel.text = "Phillipno Wheel";
}

function phillipneMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}

function phillipneClick(e:MouseEvent):void {
    gotoAndStop("mnu_Phillipno");
}

function frenchMouseOver(e:MouseEvent):void {
    txtWheel.text = "French Wheel";
}

function frenchMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}

function frenchClick(e:MouseEvent):void {
    gotoAndStop("mnu_French");
}

function turntableMouseOver(e:MouseEvent):void {
    txtWheel.text = "US Wheel";
}

function turntableMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}

function turntableClick(e:MouseEvent):void {
    gotoAndStop("mnu_US");
}
function ukMouseOver(e:MouseEvent):void {
    txtWheel.text = "UK Wheel";
}

function ukMouseOut(e:MouseEvent):void {
    txtWheel.text = "";
}
function ukClick(e:MouseEvent):void {
    gotoAndStop("mnu_UK");
}