I'm not sure there is a way you could do this through the Wizard. But you should be able to accomplish this by modifying the query manually.
In the DynamicWebChart folder, there is a data folder and inside that folder there should be a file named as follow: <your page name>_data1.php. When you open the file you should see a record set that is used to populate the chart and you should be able to modify it to get the result that you want. However, this is going to require some custom coding using Join to get the client name. If you post back with how the query i will try to help you in getting the query to return the client name.