See

http://www.xldynamic.com/source/xld.SUMPRODUCT.html
Multiple Condition Tests

for a full explanation.

--

HTH

RP
(remove nothere from the email address if mailing direct)


"Ron" wrote in message
...
I have been seeing "--" in formulae but cannot find an explanation of what
it is or does.

Example: =SUMPRODUCT(--(MONTH(B2:B13)=1), C2:C13)


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Ron P

Sometimes you're the windshield:)
Sometimes you're the bug:(