=(sumif(productlist;A12;offset(productlist;0;5))))

name of the product (computer A)

product list is the name of a column in sheet 2
(5 is the month number by the way)

formula looks for a12 in sheet 2 then gives 5th value near product list column

question
i want to find the cumulative sum 1 to 5 (for example jan to april)
how can i do

thanks in advance