Maria,

In my first response to you I suggested using one sheet for each meter,
with some header rows to store data for that meter, eg location,
description etc. You could use these header rows to record the number
of dials on the meter, as well as the multiplier for that meter. These
would always be in the same location, eg cells B3 and B4, and so you
could make use of them through absolute addresses in the formulae which
follow.

If you have 5 dials, then the meter clocks round when it reaches 99999
(or 1 less than 10 to the power 5). With 6 dials it wraps at 10 to the
power 6 etc. As you are planning to read the meters every month, then a
lower later reading implies that the meter has wrapped around, as you
won't have estimated readings which subsequently need correcting back.
Thus, your formula can take account of the wrapping and, if you can
refer to the number of dials, you can correct a negative reading by
adding back in 10 raised to the power (number of dials). The formula
from Sandy seems to be getting very complex.

Hope this helps.

Pete