This option sets the property CalendarComboBox.CLOSE_WHEN_DATE_SELECTED to true/false.
The code below shows how to do this: 
<CODE>
CalendarComboBox calendarComboBox = new CalendarComboBox();
//    close combo box when date is selected
calendarComboBox.setCalendarComboBoxProperty(CalendarComboBox.CLOSE_WHEN_DATE_SELECTED, new Boolean(true));
//    do not close combo box when date is selected
calendarComboBox.setCalendarComboBoxProperty(CalendarComboBox.CLOSE_WHEN_DATE_SELECTED, new Boolean(false));
</CODE>