How to rollback a firmware upgrade

I have a benq DW822A the bios wa upgraded to B3JC .I was playing with the BenQ_FW tool and flashed the bios to B3B7. I have tried to re-flash to B3JC but not able to, errpr message stating that the biso is not upgradable. Is there a way to roll back the update???

thanks

download the cvt files and use the win flasher to flash to 822 fw
http://dvdpro.club.st/firmware/BENQ_FW.htm