BBGA Bakers% Spreadsheet
As an exercise I created a spreadsheet for Diagram 3, Part II "Rustic Sourdough with Three Flours, a Cracked Wheat Soaker and a Yeasted Preferment.
I have no idea if it will be of any use to anybody, but here is the google doc link if you are interested.
Diagram 3 
The only difference is that I used grams instead of kg, though that is easily changed if people find that annoying.
I wanted to create a second tab that would calculate the bakers% based on inputted weights, and which would yield the same bakers% as in the the original formula (using their calculated weights) but for some reason that alluded me (no doubt due to rounding) I was unable to do this. The yeast kept giving me .003 instead of.002 no matter what I did.