I would like to create/find a spreadsheet with formulas that does the
following:

1) start with: input Sales=0, automatic OpeningStock=0, input Order=3,
automatic ClosingStock=3

2) next time: input Sales=2, automatic OpeningStock=ClosingStock of previous
session=3, input Order=1, automatic ClosingStock=2

and so on.
Can anybody help please?