Canceling Events

I have code that looks like this:

function setupEventWrapper(obj) {
old_ev_handler = obj.onsubmit;
obj.onsubmit = function () {
do_something();
if (old_ev_handler != undefined) {
old_ev_handler();
}
if (event_cancelled()) {
undo_something();
}}}

it wraps the onsubmit handler (if any) within a new function which
do_something() and then calls the old event handler.

My problem is how can I detect if the event has been canceled by
old_ev_handler(). AFAIK an event can be cancelled in three ways:

* returning false, easy to check for

* setting event.returnValue = false on IE, easy to check for

* calling event.preventDefault() on DOM

How can I check if event.preventDefault() has been called?