Refer a class from a nested movieclip

I have this class:

package {

import flash.display.MovieClip;

import flash.filters.BitmapFilter;

import flash.utils.getDefinitionByName;

import flash.filters.BitmapFilterQuality;

import flash.filters.BlurFilter;

public class cambiaBlur extends MovieClip
    public function cambiaBlur(destino) 
        var blur:BlurFilter = new BlurFilter();
        blur.blurX = 5;
        blur.blurY = 5;
        blur.quality = BitmapFilterQuality.LOW;
        destino.filters = [blur];




It blurs a movieclip.

I use this class in the main time line with this code:

new cambiaBlur(movieclip_modified);

movieclip_modified is the name of the movieclip

It works.

I want to use this class inside a nested movieclip.

I have a movieclip called:


Inside this movieclip I have another movieclip called:


How can I use the class “cambiaBlur” to modify “gift” movieclip.

In “box” movieclip timeline I used this code:

new MovieClip(root).cambiaBlur(gift);

but it fails.

Appears this error message:

“1137: Incorrect number of arguments. Expected no more than 0.”

I try with:

new MovieClip(this.root).cambiaBlur(gift);

but also fails.

Thank you in advance