I have a spreadsheet with about 1000 rows. In rows M & N there are dates. I
am trying to add in on e step the differences in the dates in column M & N
using the formula
=SUMPRODUCT(--($N$5:$N$1500$M$5:$M$1500),--($M$5:$M$1500<""),($N$5:$N$1500-$M$5:$M$1500))
This gives me a sum of 162,720. However to check the accuracy of the
formula I calculated the added the difference between each row and totaled
the numbers, that gave me an answer of 159,320. If column has a date column
B doesnt necessarily have one and vice versa. Rows with only one date shown
are ignored. Also some rows have no dates. 98% of the time column Nis
greater than column N but there are some entries where N is larger than M.
Im thinking that might be the problem. Its alright if N is larger than M.

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Robert K