"What percent of SALESPERSON 'A's' sales are also covered by SALESPERSON B?"

[#1]

PROBLEM: I have a list of 500 CLIENTS and the 10 SALEPEOPLE serving those clients. Example below.

Client Salesperson Sales

1...500 A ...J $$$

QUESTION: I would like to answer the question...

"What percent of SALESPERSON 'A's' sales are also covered by SALESPERSON B?" or

"What percent of SALESPERSON 'A's' sales are also covered by SALESPERSON C AND D?

I'm wondering if concatenating of fields may be an approach but I'm hoping for something more elegant.

Any help is much appreciated. Thanks in advance!

[#2]

Please could you describe you datamodel a bit more?

In which way, Client, Salesperson and Sales$$$ are link together?

One Table? Three tables? Or also seperate link Tables?

Thanks

Michael