Suppose you have a list of Affiliates in one column (maybe with their
ID to reference more easily). In two adjacent columns you want the
sales figures for last month and the sales figures for this month, then
you can work out the percentage change (or difference, depending on how
you class the "movement"). In a column next to that you can make use of
the RANK( ) function to tell you the ranking based on the movement.

Your sales figures could be obtained from another sheet where the
details are kept - you need to decide whether to have one sheet for
each month or one composite sheet with each month's data going across.
You may already have something at present which records the sales
figures, but your posting is not clear on this.

If you want some more specific help you will have to give more details
on what you have at present.

Hope these general comments help.

Pete