If you'd like to "see" how the DAX CALCULATE function works, then you need this tutorial. It will show you what's happening behind the scenes: How the CALCULATE function works and delivers results.

Excel – Interactive Dashboard Trick

With Pivot Charts in Microsoft Excel you can add slicers to add interactive functionality to your dashboards. But what about adding even more interactivity? You could give the user the ability to change the relevant KPI in the chart from the slicer.