Try this in an empty worksheet.

Edit|Goto (or F5 or ctrl-g)
type:
IV65536

That's the last cell on the worksheet in xl97-xl2003.  xl2007 adds more columns
and more rows.  xl95 had fewer rows.

Put this formula in that cell.
=row()*column()
and you'll see it evaluate to:   16,777,216

The 255 worksheets isn't correct.  The number of worksheets that you can have in
a workbook is limited by your computer's memory.

And if you would have typed:
IV1
or
IV2
or
iv:iv
into the name box, your attempt would have worked ok.

You have to type something that looks like an address.

Sun, 3 Feb 2008 07:09:00 -0800 from sheana
<sheana@discussions.microsoft.com>:

If you had a chart with three rows and five columns, how would you
figure the number of cells in the chart?

(By the way, the limits you cite have been greatly expanded in Excel
2007.)

Yes, letter I and letter V.  But you don't navigate a Excel worksheet
by typing things in the Name box.  When you did that, you just
created a name "IV" to refer to the current cell.  Scroll, or use F5
or Edit | Goto.  In the goto box you specify a valid row and column,
such as IV1 or IV65536.