[Greasemonkey] creating your own events

[Matt Labrum]

Hello i cant seem to be able to create custom events like i want to be able
to fire custom events that i can listen for with document.addEventListener
('customEvent',func,false)

Ive been googleing and found the following code but it dosnt seem to work

document.addEventListener("customEventThing",alert,false);

    var evt = document.createEvent("Events");
    evt.initEvent("customEventThing", false, true);
    document.dispatchEvent(evt);


it fails with the error of
Error: [Exception... "Unexpected error"  nsresult: "0x8000ffff
(NS_ERROR_UNEXPECTED)"




does anyone know of a way to make this work , or another way to fire custom
events?