Monica Rathbun shows how to show or hide clusters of columns in Reporting Services reports:
Ever had users come to you and request another version of a report just to add another field and group data differently? Today, was such the day for me. I really don’t like have multiple versions of the same report out there. So, I got a little fancy with the current version of the report and added a parameter then used expressions to group the data differently and hide columns. For those new to SSRS I’ve embedded some links to MSDN to help you along the way.
This is an easy-to-follow, step-by-step guide.