Is it possible to combine sumproduct with index or match/

I have a list of customers with area codes in A, C is overdue amounts D
amounts payable the end of the current month and E payable next month. The
headings for c,d,e is dates.
How do I tell the formula to sumproduct a column, but the column varies.
My summayr is a forcast of when recievables is due with area codes in A
descriptions in B and dates from C-AZ.
Sorry I think I have confused myself by now