Return YES only for last instance of value in a column (Google Sheets)

https://docs.google.com/a/advantagep...tHs/edit#gid=0

This is an example of what I'm trying to do. I want column A cells to check for matching email address in column G and only return YES in the last instance where the email address is found. Column A shows what I want to appear. Column B is a formula I was trying to use but isn't returning the results I need.

Column G will always be expanding. Can I format it like this so it always checks to the end of column G?

=IF(COUNTIF(G1:G,G1)>1,"No","Yes")