Bob Philips has a great page on SUMPRODUCT and double unaries '--'

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

HTH
Peter A

"Michelle" wrote:

I don't understand why sometimes I have to use "--" before an argument in
the SUMPRODUCT fuction, and sometimes a "*".

Can anyone point me to a resource that will explain why and when I have to
use these instead of just commas, so that I don't have to post any more
questions about it!

Thanks

M