Urgent: jQuery datepicker onchange event

jquery datepicker are actually triggerred by on focus event.
how can i modify the core if i want to trigger the datepicker by both onfocus and onchange event?

i do not wish to modified it one by one at my jsp, thus, im looking forward to change it in the js and register the input field with onchange and onfocus event.

Please help.
Thanls