benchmark vs selected value from slicer

Anonymous 

Here is one way of doing this.

The initial dataset I'm building on is:

 1) In Power Query (to ensure it updates) create a new table with the unique values for department and a new row for Benchmark 

 2) Create a Department Dimension table by referencing a new table to the Department Field in your main table

3) Load into the model, and create a relationship between the fact table and the dimension table. The Axis Table should remain unrelated to any other tables:

 4) Create the measures for the visual:

Sum Values = SUM('Table'[Value])

Benchmark Value = CALCULATE([Sum Values], 
                    ALL('DIM Department'[Department]))

Chart Values = CALCULATE([Sum Values], 
                TREATAS(VALUES('Axis Table'[Axis Department]), 'DIM Department'[Department]))

Chart measure = IF(SELECTEDVALUE('Axis Table'[Axis Department]) = "Benchmark", 
                        [Benchmark Value], 
                            [Chart Values])

5) Create a measure to filter the visual based on the slicer selection:

Filter Chart = 
VAR Dep = VALUES('DIM Department'[Department])
VAR BENCH = {"Benchmark"}
VAR NewT = UNION(Dep, Bench)
VAR CHART = VALUES('Axis Table'[Axis Department])
RETURN
COUNTROWS(
    INTERSECT(NewT, CHART))

6) Build your visual using the axis table department field as the x-axis & the [chart measure]. Add the slicer from the DIM department. Finally, in the filter pane, in filters for this visual, add the [Filter Chart] measure to the Axis department, select TopN and set the value to 1:

I've attached the sample file for your reference