Dynamic naming

Hi, this is not working and i don't understand why.

First i add an eventlistener

var couverture_out=rollout.bind(this,'couverture');

this.couverture.addEventListener("mouseout",couverture_out);

then, i want to remove it on a click on the object

this.couverture.addEventListener("click", obj_bon.bind(this,'couverture'));

function obj_bon(obj) {

    var obj_out =  [obj]+"_out";  /* give 'couverture_out' */

    this[obj].removeEventListener("mouseout", obj_out);

}

this[obj].removeEventListener("mouseout", obj_out);

should give

this.couverture.removeEventListener("mouseout",couverture_out)  but that is not working, mouseout is still active

thanks for your help