DateField customization

I'm unable to find a way to customize the underlying DatePicker that DateField uses. At the very least, one should be able to change the starting day of the week and attach the 'onchange' event on the text field so something can happen when a date is picked from the popup calendar. The only workaround I've come up with is to pull the datefield.js out of the Tapestry jar and hard-code the starting day of the week. I'm still working to getting the onchange event of the text field to fire.

Perhaps there is an easy way to do this without actually needing a fix - if so, perhaps all that is needed is a quick wiki howto.