Time to learn about subqueries. Here's an intro:
http://allenbrowne.com/subquery-01.html

You will end up typing an expression like this into a fresh column in the
Field row in query design:
(SELECT Max([Visit_Date]) AS PriorVisit
FROM [Table1] AS Dupe
WHERE (Dupe.[Account_No] = [Table1].[Account_No])
AND (Dupe.[Visit_Date] [Table1].[Visit_Date]))

--
Allen Browne - Microsoft MVP. Perth, Western Australia
Tips for Access users - http://allenbrowne.com/tips.html
Reply to group, rather than allenbrowne at mvps dot org.


"slotmgr70" wrote in message
...
I have a table that tracks each customers visit to my store. I hold
promotions on occaision that bring customers that haven't visited my store
in
awhile. When I hold a promotion, I'm trying to determine the number of
days
since the last visit for each customer. For example, here is a sample
customer:

Account_No Visit_Date
1234 4/19/10
1234 4/10/10
1234 3/10/10
1234 2/13/10

This customer generally visits once a month. Assuming that I held a
promotion on 4/19/10, I want to calculate the number of days since the
most
recent visit, in this case being 4/10/10 (9 days).

The goal is to see if I have affected their trip pattern by holding the
promotion and if I was able to generate an incremental trip by holding the
promotion.