RadPivotGrid provides tooltips with information about the hovered cell's value out of the box:
You can handle the cell's clicking and get the aggregated value. The following forum post is quite useful on this topic: https://www.telerik.com/forums/how-can-i-get-selected-cell-value#2qeXovBdSkme0nFBxKoCLw
However, I suppose that you need something similar to the drill down functionality that RadPivotGrid offers: https://docs.telerik.com/devtools/winforms/controls/pivotgrid/drilldown
Thus, utilizing the GetUnderlyingData method you can extract the records from the data source object responsible for accumulating the result for a particular row and column. The GetUnderlyingData method is working with two parameters: Row Group and Column Group. Then, you can display the relevant data in a RadGridView. Please refer to the above referred help article which is quite useful on this topic.
I hope this information helps. If you need any further assistance please don't hesitate to contact me.
Dess | Tech Support Engineer, Sr.
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