Great information on Sumproduct. Thanks for the posts. I am befuddled by one aspect of Sumproduct, that being whether the {} are really needed. I've seen some pages that stress that they need to be included and others that state specifically that they do not. My Sumproduct formulas seem to work fine regardless of whether they are included, so I tend to omit them. But, if there is some technical reason they should be there I'd like to know why.