How can I display all selected members in a multi-select prompt, on a text header?

Summary: I am trying to display all of the individual selected members that are chosen in a multi-select prompt, on the header of the report, in Narrative Reporting. The purpose is to show the user what selections were made, without having to go back into the report prompt.

Content (please ensure you mask any confidential information): first screenshot is the multi-select prompt, with three selections made. The second screenshot is the formula being used to reference the prompt selections (MemberAlias function, with the Grid Name, Dimension name and the row where the prompt is in the Grid) . he third screenshot shows the header text after the report is run. No matter what is tried, the function ONLY returns the first selection made in the multi-select prompt.