This will do what you want. Adjust ranges accordingly.

=SUMPRODUCT((A1:A10="")*(B1:B10=1))


HTH,
JP


On Mar 27, 1:46*pm, Libby wrote:
Hi there,

Column A has in it a list of dates. It's quite a long list but some rows are
necessarily blank.

For the same number of rows, each cell in column B has a number in it.

Is there a formula that will display in one cell, say C1, the total of
number of 1's that occur in column B where there is a blank in Column A.

Many thanks in advance.