SELECTEDVALUE with multiple selection

[powerbi2srm]

I've created a table in Power BI (Comparacion Ventas/Margen with two records in a column named "Medida": "Comparar con el margen" and "Comparar con las ventas":

I'm looking for when I select "Comparar con el margen" in a slicer, it shows me the calculated measure "margin" and when I select "Comparar con las ventas", it shows me the calculated measure "sales".

I get this result by creating two new measures:

margin (selection) =
IF( 
  SELECTEDVALUE('Comparacion Ventas/Margen'[Medida])= "Comparar con el margen",
  [margin], 
  BLANK() 
)

sales (selection) = 
IF( 
   SELECTEDVALUE('Comparacion ventas/margen'[Medida])= "Comparar con las ventas", 
   [sales], 
   BLANK() 
)

This works properly as long as I select only ONE option.

When I select the two options I get a blank result. You can check it in the following three photos:

Selecting marginSelecting sales

Thank you so much!

[johnt75 · Accepted solution]

Use a field parameter instead, they were specifically designed for this situation.