Globally add spinners to AJAX calls

Is there any way I can globally add some JS code to all my AJAX calls
to implement user feedback - indicating that his action is being
processed?

Something like automatically disabling the submit button and showing a
spinner would be great.

Thanks,
Amir

http://garbageburrito.com/blog/entry/30/automatic-ajax-loading-images-with-prototype

Thanks, great article!

Amir