Comparing columns in excel - can't remember??

Winkfield Posts 1 Registration date Friday March 11, 2016 Status Member Last seen March 11, 2016 - Mar 11, 2016 at 12:27 PM
I used to do this function years ago and can't remember how now!
I have three columns and each contains a value similar to A001187. I want to compare the three and list the differences where one value occurs in column A that does not in column C or E.