I actually need some assistance with two things.

#1. How do i locate duplicates in a single colum on a single sheet? For
example i have a file with over over 10, 000 customers. I want to do a
duplicate search ONLY on the email column. How can i get excel to
identify duplicates in that column only.

#2. These customers have expire from my program and i have dates that
they will expire. Is there a formula that can be implemented to change
it from a false to a true after the date is reached? So if they expire
tommorrow,,,,, it changes from false to true on its own with out me
mannually doing it?