ActionScript 2.0 :: Remove OnRelease Event For MovieClip

I'm trying to remove a onRelease event for a movieclip of mine. The action is defined in the movie's class file like so:

Code:
private function onRelease():Void {
delete this.onRelease;
trace ("test");
}

Unfortunately this doesn't seem to be removing the onRelease events, and whenever I click on the button it traces "test". Is there some other way to remove onRelease events when they are applied through a class? When I use the above method out of the class definition all is fine, like this:

Code:
secaoMap_mc.onRelease = function () {
delete this.onRelease;
trace ("teste");
}