Designing a client database

Hello all,

I am trying to design a database to store the information of our clients. I
would like to get some inputs from you guys on the design. Also whether
anyone knows of a web site that I can go to download a sample client
database.

I am facing some difficulties on the design. I will discuss my difficulties
below.

Before I share with you my difficulties, the way we have our client number
is different from most firm. Our client number is not automatically
generated by Access. Instead we come up with a new client # whenever we add
a new client. The structure of our client # is, for example, "1234.01". The
first 4-digit represents the family and the last 2-digit represents the
clients in the family. For example, if we do a job for both father and son,
the client # for the father is 1234.01 and the son is 1234.02.

In the past, the database was wide-open, and people would go into the table
to add a new client. For example, if it is a new family, people would look
up the whole table and come up with a new client # by picking the unused
client #. That whole process created big problems because there were no
controls on the database.

Now I am trying to re-design the database where people use the forms to add
new clients or modify existing clients.

The difficulties that I am having is how do I design it so that:

1. the user can easily come up with a new client # for a new client
2. the user does not end up creating the same client with a different
client #

Thanks in advance for your help. Any suggestings or comments are greatly
appreciated.