How to get access to event object?

How to get access to event object inside Calendar event?

myCalendar.attachEvent("onClick", function(date){
    // your code here



you have to add one more arg (i.e. window.event) for callEvent() in calendar source file.

I would prefer to not edit source code. Can I override callEvent() from my code?

You have to override function which call callEvent() to add one more param into it.