Dynamic Column Headers

I have a use case for column headers to change based on the selected value of date slicer.  I am trying to work around this currently by using field parameters to display my different measures.  My idea was to create VAR P1 = DATEADD(LASTDATE(), -1, Month) and replace the title in field parameters with said variable.  LASTDATE() in field parameters doesnt respect the Date slicer filter in my report and returns the End of Year.