I think this ia a very straightforward question.

I have a column of the number of items sold, each month a new column
is added. at the bottom of each column is a grand total for the month
in the form of
=D14:D36

however if there are no items sold during the month then it returns

#VALUE!

If there are no sales then I would like it to show either 0 or just an
empty cell.
How can i achieve this please.

Bob