outerClick.js

// Add an outer click Event to an Element
// http://cpojer.net/blog/Custom_outerClick_event (but this page doesn't exist anymore)
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);
    }
	
};

outerClickExample.js

$('test').addEvent('outerClick', function(){
    // you clicked outside $('test')
});