ISSELECTEDMEASURE Used by expressions for calculation items to determine the measure that is in context is one of those specified in a list of measures.
Syntax
ISSELECTEDMEASURE( M1, M2, ... )
Parameters
M1, M2, … – A list of measures.
Return Value
This function currently applies only to SQL Server 2019 Analysis Services CTP 2.3 and later.
Reference Data
https://docs.microsoft.com/en-us/dax/dax-function-reference