Microsoft Reporting：检查是否存在某个值

Using Microsoft Reporting Services, with local processing mode. Loading data sources and everything works nicely. What I would like, is to, in the the report definition, check if a certain value exist in on of the data sources. Is this possible? Like, if I have a data source with just one column of "Name". Can I somehow check if the name "John" exist among the loaded data?Using Microsoft Reporting Services, with local