You can save your BIAB style to midi and use EMC's Style Works to convert the midi to a Yamaha style or you can find out how Macaddict makes his Korg styles and use the same software to convert from Korg to Yamaha styles.

Have a look at EMC's product:
[url] http://www.emc-musicsoftware.de/viashop/storefront/start.asp? [url/]
Andre