I have one customer-list showing which of our customers have been active the
last year (list1), and one list showing all of our customers and their
adresses (list2). I want to send out a letter to all of the customers who
have been active the last year.

Both lists are sorted by customer-numbers. So list2 has the whole range from
100001 to 117950, and list1 shows approximately 4300 of these customers have
been active in 2008 or 2009. I don't want to waste money on sending out
letters to all the inactive customers, so..

Is there any way for me to sort list2, based on customer numbers, so that it
only shows the customers present in list1?