The best option is to just do it manually, as it does not seem to happen often. Especially if you use the RDLC editor in VS2008.
You can use the Matrix control instead of the Table control. The matrix will - based on the grouping - generate the corresponding columns and rows. You will have to change your request and it will be a little slower.
You can use a Table or List control with parametrically hidden columns.
You can automatically change the XML report report depending on how many columns you need. Since RDLC is an xml file, this is trivial.
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