Try this...

=A1+A2+A3+IF(COUNT(A1:A3)<3,A4,0) +IF(COUNT(A1:A4)<3,A5,0)

The values of A4 and A5 are only included if there are less than three
numbers in the cells above them.

Hope this helps.


--
mrice

Research Scientist with many years of spreadsheet development experience
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