Finding the right function, totalling customer recency.

I'm new-ish to Excel so I'm sorry in advance.
I'm trying to learn how to create a RFM(receny frequency monetary) analysis, but i'm stuck and I've been plucking at my hair for hours.

So in my spreadsheet I have a list of customer ID's which are in monthly trasnactions. For the full year I have repeat customers, I'm just trying to find a function that can tell me the customer ID and the last date they were there altogether.

Thanks for any help, I really appriciate it!!

OK... assume your list of customer ID's is in column A (A1:A100), and your dates are in column B (B1:B100), and your list is in order by date, you can try this:

=LOOKUP(2,1/(A1:A100="xyz"),B1:B100)

Where you can substitute your customer ID for xyz. Or, you could use a cell reference instead of "xyz", if the ID you are looking up is in another cell.

Format the result as a date.

- Moo