Give this query a try and let me know if that's not what you are looking for.
SELECT DISTINCT Customer.CID, Customer.CName, Purchases.Item, Purchases.Total, Purchases.Date
FROM Purchases, Customer
WHERE Purchases.Date=(SELECT MAX(Date) FROM Purchases WHERE Customer!CID =Purchases!CID)
The SELECT MAX part is just a subquery. All it does is find the Last purchase date that matches the current CID and then uses that as a criteria for displaying the record.
Think of the query as two separate queries.
The first one just selects (I think that the proper term is 'projects' but college was too long ago at this point) the records from the two tables - Customer and Purchases. At this point you would have all the purchases from the Purchases table.
The subquery further restricts which row to display. It's kind of like using a WHERE Date = #1/1/2008# but since you don't know what the date is you use the subquery to find the Max date and you use the Customer!CID =Purchases!CID to make sure that the subquery returns the correct date for the CID that was projected from the first part of the query.
I hope that makes a little sense and doesn't complicate things more for you.