Use the CountA function

=COUNTA(Sheet1!A:A)
=COUNTA(Sheet2!A:A)...

This will return the count of cells with non-null values
in column a of sheet 1, sheet 2, etc. If you add or
delete a value, this formula will automatically reflect
the new count. Of course you will have to pick a column
which always has a value for each machine in your list.

-----Original Message-----
I have an Excel file with four worksheets. In each
worksheet is a
list of computer names which can total 1,000 per
worksheet. I want
to create a new worksheet that lists just four numbers:
the total
number of computers/lines in each worksheet. Is that
something I can
do with a function?

I'm hoping that as each worksheet gets updated,
the "report" worksheet
will automatically update its numbers with the new
totals in the other
four worksheets.
.