Slider expression

I have two visualizations. One is a bar graph and the other a cross table.

The cross table data is limited per marked item in the bar graph. The bar graph™s category axis is a hierarchy. Levels A, B, and C.

I want to create an expression to only show data in the cross table is hierarchy C is selected (when using the slider, not filter)

I need help with the underlined expression below.

Case when (syntax œif C is selected in Graph)  then true else false.

Thanks in advance. 

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