checkpoint for duplicate invoices

dup.jpgHi.

I'm just doing some annoying entry work and wanted to figure out this problem I cant seem to get.

Pretty much the client sends us Purchase receipts that are really really messy. Some of the receipts can lead to duplicate entries if not careful because they are sending us 1) a receipt 2) a delivery notice with for the receipt that looks really similar to the actual receipt if you are not careful reading it, which has the same invoice amount as the receipt.

Its a ton of invoices and going forward I'm trying to add-in a formula that checks whether I have entered a duplicate invoice by accident.


I.e in column A for Excel I just count tabs of all the receipts so that I can get the Purchase Total for the Month i.e 101.15, 3023,13, 232.15, etc etc etc....

Would like to have in the column left of it something where if I notice 101.15 is enter twice (101.15, 3023,13, 232.15, etc etc etc....101.15), a notice of possible duplicate is given. Ex the two values highlighted in green in the screenshot...I was thinking of using some variation of Vlookup, match, countif, or count to figure out how to do this but wasnt able to come up with anything good.

Could I get some help with this?

Best,
DK54

Have a look at the conditional formatting formula in column A of the attached.
This is one way of doing it.