Originally Posted by joeu2004[_2_]

"KeriM" wrote:
I had an empty cell in the range (since Jan 1st was a holiday),
so sumproduct wasn't working. I thought the "--" would negate
any empty cells, but I guess not?

No, it does. A truly empty cell is treated as zero.

My guess: what you are calling "empty" is actually a formula that returns
the null string (""). The null string is text; --text results in a #VALUE
error.

One other explanation that is unlikely, but possible: what appears to be
empty actually contains a __constant__ null string.

For example, enter ="" into a cell, copy it, then paste-special-value into
the same or different cell.

The cell will look empty; but ISBLANK(A1) returns FALSE. Of course,
ISBLANK(A1) returns TRUE for a truly empty cell (no formula and no constant
value).