I was able to run the program in MS Excel. I noticed in the material needed the length didn't have the unit but the width did have the mm unit. I tried inches in place of the millimeters and it seems to work. Have you checked to see if that works for you? Metric is no problem and it's what I use though.

It's nice to have and I hope to use it soon. I've been making mine in CAD which take a lot of time. I was wondering if the spreadsheet could be used to make a graphic drawing of a bellows side in 2D? That would be super.

Thanks for the work,
Curt