You can do this in two different ways.
1. Group by client name. Put the client name in the group header and the position in the details. If the data must be lined up so that post 1 is next to the client name, go to the Section Expert and turn on "Underlay Following" for the client group header section.
2. Right-click on the client name in your report and select "Format Field". On the Common tab there should be an option to "Suppress if duplicated".
-Dell