The ONLY available software for creating styles on recent Roland arrangers is from EMC in Germany, Style Works 2000 & Style Factory:
http://www.emc-musicsoftware.de/viashop/storefront/start.asp?

Style Works 2000 is much more comprehensive but also costs a lot more than Style Factory.
Either program will do the trick and can be ordered directly from EMC.

Good luck!

Michael