Very kind of you J_T.
At the moment I only intend modifying the basic spreadsheet the boss has done by replacing a scanned image of the envelope with a plotted graph. Not sure how successful I'll be but it's something to do while waiting for the passengers.
He's not hugely PC or spreadsheet literate & I'm no huge expert either. He's already incorporated some simple conditional formatting changes I suggested are possible to red flag out-of-limits conditions - hence the need for the sloping forward face calculation to complete the test.
Eventually I think he plans to use PDAs for this sort of stuff so a simple spreadsheet is all it will be.