Crystal
I have no idea how to do the second part that you mentioned about using
arthimatic to create a model and entering that into the spreadsheet
data so I'll probably end up isolating the chunk of the graph that fits
the correction volume I need, getting the equation of the line and work
from there with pen and calculator.

That's a kind of model, just a local one restricted to the area you're
interested in :-) By using the spreadsheet I just meant using the
formulas in cells the way you would punch numbers into your calculator.
I miss my old calculator, but since it died I never bought a
replacement. I just start up Excel instead and doodle as if it were a
pen and paper with a calculator built in.

--
Del Cotter
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