Hi Rob

For starters, when you are using Access, you can't think in terms of Excel.
This is known as "commiting spreadsheet", which is a heinous crime in
the Access world <g>.

You are actually on the right track, at least in as much as you have realized
that you are going to need three tables. Where you're going wrong is
trying to store data like customer names and part numbers redundantly
in the third table. All you need in there is ID numbers as foreign keys
and perhaps some fields that are specifically related to a purchase,
such as purchase date.

Basically, what you have is known as a many-to-many relationship
between customers and parts (a customer can purchase one/many
parts and a part can be sold to one/many customers). An example
table structure would be like;

tblCustomers
**********
CustomerID (Primary Key)
LastName
FirstName
other fields related to customer

tblParts
******
PartID (PK)
PartNumber
PartDescription
other fields related to parts

tblPartSales (junction table to define the M:M relationship)
*********
CustomerID (Foreign Key to tblCustomers)
PartID (FK to tblParts)
PurchaseDate

Then you would, for example, create a main form/sub form where
the main form would be based on the Customers table and the subform
would be based on the junction table. In the subform you would have
unbound controls that would *display* the appropriate part information
based on PartID.

Here are some links where you can find some excellent tips and
tutorials on Access, and feel free to post back here when you have
more question. Good Luck :)

http://www.accessmvp.com/JConrad/accessjunkie.html

http://allenbrowne.com/tips.html

http://allenbrowne.com/casu-22.html

http://www.mvps.org/access/