Update calculated column or filter based on slicer?

I have a complex org hierarchy that isn't realistic to turn into a table (would result in something like 2 million+ fields), but would like to use a manager slicer to retrieve all hierarchy members below them when selected. 

For example, you have employees A, B, C, D, E and F. 

A and B report to C

D and E report to A

F reports to B

If I select C, I want to see the results for B, C, D, E, and F.

I've done this before in role security using PathContains(Path(employee, manager), username) and built a similar measure column to retrieve the slicer value (IE, if you select A, it returns A, B returns B etc.), but as calculated columns are initialized on load, it doesn't change as the value changes. Is there any way to re-initialize the column or do this somehow without blowing up my whole report and redoing every measure and display to use some sort of complex calculate?