the problem I\'m facing is this:
The "onchange" is only fired when the attribute is programmatically changed or when the user makes a change and then focuses away from the field.
Have you looked at using YUI's calendar object? I've coded up a solution that puts the yui calendar inside a yui panel and hides the panel until an associated image is clicked. I'm able to see changes from either.
http://developer.yahoo.com/yui/examples/calendar/formtxt.html