Finding the max of multiple repeating customers using vlookup

[uwajes]

I'm working on a customer data conversion for over 7000 customers. In my file I may have the a customer to show up only once or up to 80 times (multiple addresses for same customer). So I have to determine which of the customer addresses is the "primary customer" by flagging it with a "Y" for those that have the highest sales amount.

So in the attached spreadsheet, I have 3 columns.
Column A - Customer #
Column B - Sales amount
Column C - Primary (top customer address)

Any ideas on a formula I can use in column C?

[DonkeyOte]

If, as implied by your sample, the data is sorted by A and then B (desc) then simply

C2: =IF(C2<>C1,"Y","")
copied down

EDIT: though I suspect you get more value from

C2: =IF(C2<>C1,A1&":Y","")
copied down

You will subsequently find it quite easy to extract the address for a given supplier by simply searching Column C for "customer:Y"

[uwajes]

I think that is going to work well.

C2: =IF(A2<>A1,A1&":Y","")

Thanks for your help!