My data is arranged in three columns: Col a is my inventory
count date, Col b is a code letter (a,b,c or blank), col c is my
sales.
col a col b col c
s04 a 10
f04 b 12
s05 c 13
f04 a 10
s04 a 12
f04 (blank) 9

I need to sumif all numbers in column c where column a and
column b match (for example: col a has 2 s04 where col b has
an A so I need the total of 10+12. I suppose I could
concatenate A+B, and then sumif on that, but is there a
better way? Thanks for any help.