Hello Fernando, I've written a program - GEFFEM - to calculate Sun's multiple ephemeris with a great precision. The program is in Italian but I think you can understand and use it very easily.
You can download it from the Mario Arnaldi's Internet place http://digilander.iol.it/McArdal/Gnomo-index.htm select > Software > Astronomia > Geffem Regards - Gianni Ferrari
