Multiple AttachEvent On Document?

Does anyone know of a way to attach multiple events to the document element?

I have a class that when initiated attaches events to the element it effects but also attaches an event to the document element.

If my class is declared more then once, only one of the classes will be effected by the event (on the document element) where as I need both.

this.addEvent = function(obj, type, fn )
{
if(obj.attachEvent)
{
obj['e'+type+fn] = fn;
obj[type+fn] = function()
{
obj['e'+type+fn]( window.event );
}
obj.attachEvent( 'on'+type, obj[type+fn] );
}
else
obj.addEventListener( type, fn, false );
}

I presume it works fine on Firefox because addEventListening allows multiple assignments where as attachEvent doesn't.