I Think it behaves in a weird way because you're using .getselectedmember with data cell selection in the crosstab.
You said previously that you are using data cell with columns. This means that your selectedMember in the crosstab should be the column (which as far as I can tell, doesn't contain userID).
As previously stated you should use rows, highlighting can be done by fetching the name of the measure in the datacell from getselectedmember.







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