Comparing numbers in lists/columns of numbers

Is there a way of finding which number(s) appear in two lists/columns of numbers?

Here is an example of what I mean: Column 1 contains the ID of donors who failed to pay their monthly donation to a charity in January. Column 2 contains the ID of donors who failed to pay their monthly donation in February. The aim is to find donors common to both lists/columns - those donors who have not paid in consecutive months - so that notifications can be sent to those donors informing them that they have failed to pay their donations in two consecutive months. (I work for a large charity organisation in Sydney, NSW, Australia).

Your help would be very much appreciated.

Onesimus

Hi and welcome to the board

an answer to your question can be found here :http://www.cpearson.com/excel/ListFunctions.aspx

HTH

Thank you arthurbr for your very quick reply!

Onesimus

Glad to help
Cheers