Customizable Joomla 1.5 default date picker

I require the default joomla date picker to be customizable, so either customize what is there already or add a new jqeury calender. Basically I have used the virtumart hack that calls the default joomla date picker which works fine but i need certain days/dates to not be selectable such as weekends, bank holidays, plus the user should only be able to select a date that is three days from the current day. Hope that makes sense.