The ISERROR function returns an array of TRUE or FALSE. The double unary
coerces these to numeric 1 and 0:

--TRUE = 1
--FALSE = 0

Then SUMPRODUCT adds them up for the result.

See this:

http://xldynamic.com/source/xld.SUMPRODUCT.html

--
Biff
Microsoft Excel MVP


"diepvic" wrote in message
...
Thanks Jacob & T.Valko,

It works so perfectly
Anw, could you pls explain for me how it works? What does "--" mean here?

Thanks a lot