Check if value is in a List

Hello everybody!

How can I find out if one of the selected values is a string?
What I tried out:

VAR SelectedKpi = SELECTEDVALUE(KPIs[Value])
return
IF(SelectedKpi IN {"SOE"},SUM(...),BLANK())

It works, but I select multiple values, it will only work for one at a time. 
I would like to be able to check if the string is into that variable.

Thanks!