I have a current customer list in Excel 2010. I have other lists I want to mail or e-mail to but do not want to include those already on my customer list. Eliminating duplicates does not work. I want to eliminate the names in other lists that are already on my customer list. Lists are too big to do by sorting and deleting.

I had a formula once - but can't find it - it was something like -

=IF(OR(TRIM(A1)=TRIM(A2),TRIM(A2)=TRIM(A3),**,TRIM(A2))

But this doesn't work.