One possible solution is the software Dan suggested (in response to your most recent posting). Another is the AVR programming software available as open source.

Although I'm still happy to share my code (offered elsewhere), I would have to think that the open source software would be a better starting point, since it has at least had some public scrutiny and saves me the embarrassment of letting out something that I pounded out in a pinch when the 'S8252 first became available.