Is days to complete a field in a related table or a repeating field?
Sum (Days to Complete)/Count (Days to Complete)
is the same as
Days to complete / Days to complete
which will be 1 in every case where Days to complete is not zero or empty.
Taking your expression at face value....
Sum (Days to Complete)/ Max ( Count (Days to Complete) ; 1 )
Should eliminate the divide by zero error. But you might also take a look at the Average function.
(Days to complete)/Count(Days to complete) did the trick. Thanks a million!!!