Movie clip trouble, help plz???

ive made a character that move with the arrow keys. i can change the movie clip so that when a button is pushed down it goes to a walking frame but i duno how to make it go back to the standing frame when button is realeased and the characters not moving.

here is the code :

onClipEvent(load){
speed=5;
}
onClipEvent(enterFrame){
if(Key.isDown(Key.LEFT)&&Key.isDown(Key.UP)){
this._x-=speed;
this._y-=speed;
this._rotation=315;
this.gotoAndStop("walking");
}
else if(Key.isDown(Key.LEFT)&&Key.isDown(Key.DOWN)){
this._x-=speed;
this._y+=speed;
this._rotation=225;
this.gotoAndStop("walking");
}
else if(Key.isDown(Key.RIGHT)&&Key.isDown(Key.UP)){
this._x+=speed;
this._y-=speed;
this._rotation=45;
this.gotoAndStop("walking");
}
else if(Key.isDown(Key.RIGHT)&&Key.isDown(Key.DOWN)){
this._x+=speed;
this._y+=speed;
this._rotation=135;
this.gotoAndStop("walking");
}
else if(Key.isDown(Key.LEFT)){
this._x-=speed;
this._rotation=270;
this.gotoAndStop("walking");
}
else if(Key.isDown(Key.RIGHT)){
this._x+=speed;
this._rotation=90;
this.gotoAndStop("walking");
}
else if(Key.isDown(Key.UP)){
this._y-=speed;
this._rotation=0;
this.gotoAndStop("walking");
}
else if(Key.isDown(Key.DOWN)){
this._y+=speed;
this._rotation=180;
this.gotoAndStop("walking");
}

}

Ive tryed to put
this.gotoAndStop("standing");
at the top before the code an at the botton but it doesnt work .
plz can someone help me out, i hav no idea.

Nice one.

Zac