Maybe I don't understand your question properly but will the following work
for you?

=COLUMNS(A1:F10)

Where A1:F10 is the range that makes up your nxm.

Hope that helps.

Bill Horton

"Jerry W. Lewis" wrote:

I have an nxm rectangular range of cells, for which I want to determine the
largest columnwise data span ("range" in statistical terms). Clearly, I can
do this using a row of m helper cells each containing
=MAX(column)-MIN(column)
with the desired result then given as =MAX(helper_row).

Can this be done in a single cell without the helper row?

Jerry