problema con scroll de imagenes

[nelsongn]

TEngo un problema con un scroll de imagenes, tengo el scroll dentro de una mascara la primera imagen el la acepta dentro de la imagen pero despues el codigo hace que la imagen se duplique y pase por encima de toda la pelicula osea, sale de la mascara, como hago para mantener todo dentro de la mascara?? a continuacion le dejo el link de la pelicula y el codigo:

http://www.gravityweb.com.ve/movie.swf

Código:

//initialize
onClipEvent(load){
percent_increment = .025;
addstrip2 = false;
}


onClipEvent(enterFrame){
// this is it! only one line of code!
this._x += (_root._xmouse - 320)*percent_increment;







//now, in order to have a seamless strip
//you have to tell the movie (1)when to duplicate the strip and (2)whether to put it on the right or left side


//when moving left...
//add strip2 to the right side of the strip if the strip is less than 0
if(this._x <=0 && this._x >= -this._width){ 
//only add it when addstrip2 is false otherwise it will contiually add strip2
	if(addstrip2==false){
		this.duplicateMovieClip("strip2",1);
		addstrip = false;
	}
//position strip2
//subtract 1 cause the border will look wide when it's put next to the other border
	_root.strip2._x = this._x + this._width-1;
	_root.strip2._y = this._y;
}
//once the strip has moved off the screen(left side),take it and put it on the right end of strip2
if(this._x <= -this._width){

		this._x = _root.strip2._x + this._width - 1;
}





//when moving right... (same code as moving left but checking for different positions)
if(this._x >0 && this._x < this._width){ 
	if(addstrip2==false){
		this.duplicateMovieClip("strip2",1);
		addstrip = false;
	}
	_root.strip2._x = this._x - this._width + 1;
	_root.strip2._y = this._y;
}
if(this._x >= this._width){
		this._x = _root.strip2._x - this._width + 1;
}
}