Hi,

It is one of several ways of getting the results of the Isnumber function to
be stated in terms of 1 and 0 instead of True and False, so that they can be
used in the calculation

There is a full explanation at
http://www.xldynamic.com/source/xld.SUMPRODUCT.html

Anthony

"M Moore" wrote:

Could someone explain the purpose of a double negative in the following
formula:

-sumproduct(--Isnumber(match($a$2:$a$15000,Namedrange,0))

Thanks.