I would be obliged for help in setting up a formula, or
similar, relative to retaining a 'running total' in 2
different worksheets please.

e.g. in sheet 1 (cell 1a) - inputting a new figure every
week.

in sheet 2 (cell 1a) - to protect and record the sum of
all the previous weekly figures accumulatively over the
usage period, month, year and so on.

Thanking you