Adding an event listener to an iframe

Is it possible to add an event listener to an iframe? I've tried this code, but it doesn't seem to work:

document.getElementsByTagName('iframe')[0].contentWindow.window.document.body.addEventListener('afterLayout', function(){
                console.log('works');
            });

I've also just tried using getting the element by id and adding my listener via the JavaScript framework I'm using, like this:

Ext.fly("iframeID").addListener('afterLayout', function(){ alert('test'); });

I can call functions in the iframe, so I don't think security is an issue. Any ideas?