» Retrieving List Values that Do Not Appear in a Second List

Problem:

We want to create a new list consisting of the values from List1 (column A) that are not common to List2 (column B) as well.

Solution:

Use the INDEX, SMALL, IF, COUNTIF, and ROW functions as shown in the following Array formula:
{=INDEX($A$2:$A$7,SMALL(IF(COUNTIF($B$2:$B$7,$A$2:$A$7)=0,ROW($A$2:$A$7),1000),ROW()-ROW($C$2)+1)-ROW($C$2)+1)}
Enter the formula in cell C2 and copy it down the column until the #REF! error is returned.