If the only possible options are Mar and May then:

=IF(K2="Mar",SUM(A2:AC2),SUM(A2:E2))

If K2 can have any month, then you would need something with the MATCH
function
--
Gary''s Student - gsnu200748


"Lisa" wrote:

I need help with the formula.

A B C D E
1 Jan Feb Mar Apr May
2 10 5 15 7 8

If K2 is Mar I need to sum A2 thru C2. If K2 is May I need to sum A2 thru E2.

Thank you in advance.