Column A has over a hundred different parts codes. The order of codes in this can change from month to month.

Column C is a list of all the parts codes from all invoices in Janaury with their sales value in Column D. These columns are a couple of thousand lines long. Columns E through Z contain the rest of the months of the year, with a list of parts codes off the invoices in the respective months and their values.

If I want to find out the totals for the codes in say January I use a sumif formula in column B. But if I want to find out the totals for March I have to re-wrtie the formula. Is it possible to have the formula look up the values from a month declared in cell A1?

Thanks for any ideas.