List of headcount at any point in time

[Newbie777]

Hello,

I am using the measure below which can calculate the number of employees at any given point in time.  

The measure above also can produce the list of employees when put in a table with name of employees as dimensions.  However, the time dimension is not clear which one is used, and I'd like the default time dimension in the measure above to be the today's headcount, and it should respond to the selection in other periods in other charts.  

However, when I input the set expression below in the measure expression above, it doesn't work.  I'd appreciate it if you could let me know how I can get the list of today's headcount as a default which responds to selections in other charts for the past periods flexibly.  

{<[Date Copy]={$(=max([Date Copy]))}>}

Thank you for your help!