Element.Events.outerClick

outerclick.js

Element.Events.outerClick = Element.Events.outerClick || {
    base : 'click',
    condition : function(event){
        event.stopPropagation();
        return false;
    },
    onAdd : function(fn){
        this.getDocument().addEvent('click', fn);
    },
    onRemove : function(fn){
        this.getDocument().removeEvent('click', fn);
    }
};