I am facing a request to find out the fastest growing/declining items in sales in past X period where an end user could pick up from a time list box. Let us say, last 12 weeks. I have weekly sales per item per store on hand, total around 10000 items, 100 stores. relatively a big sheet.
I am lost in constructing the expression. It looks need compare each item with each other by weekly sales per store in same period. Can anyone could shed some light? Many thanks.
