By the way:

The latest update of the spreadsheet, including very detailed instructions are now available.

You'll find it here:

http://www.waybeyondmonochrome.com/WBM2/Library.html

and here:

http://www.darkroomagic.com/DarkroomMagic/Darkroom.html

The spreadsheet is now fully compatible with 21 and 31-step Stouffers. The instructions could use another English edit, but that would have delayed posting by another week. I hope it helps and you will report back with any issues you may have, so, I can improve it for future use.