The name of the css class to be applied to this instance of the summary. This property is meant to be used for conditional formating based on the value of the summary, when it
SummaryCalculated event is raised for the standard summaries or the
CalculateCustomSummary event is raised for the custom summaries.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2