You have two long columns of similar data and you want to find differences, if any. Assuming the columns are A and B, in cell C1 enter this formula
=IF(ISERROR(MATCH(A1,B:B,0)),A1,””)
and copy it down column C as far as the data goes. Click Calculate in the Formulas tab and column C will display all the items that appear in column A but not column B.