private static CalendarEventEntry addExtendedProperty(
CalendarEventEntry entry) throws ServiceException, IOException {
// Add an extended property "id" with value 1234 to the EventEntry entry.
// We specify the complete schema URL to avoid namespace collisions with
// other applications that use the same property name.
ExtendedProperty property = new ExtendedProperty();
property.setName("http://www.example.com/schemas/2005#mycal.id");
property.setValue("1234");
entry.addExtension(property);
return entry.update();
}