Noam,
There's an easier way to handle the Jewish Holy Days. Create your modifed file, save it with a different name, and then load it whenever you need it.That way, you don't have to constatly modify the main file.
I have 4 different .ahx files for certain times of the year. When I need to change, I simply run AHP, clear the interface, open the file I want to use, and download to the interface.