Problem in KPI parallel period

Hi everyone, can you kindly check this code. It returns a null value. I'm just trying to learn SSAS but KPI it's going to make me crazy. Thank you. 

Case
  When (([Measures].[Sales Amount]-[Measures].[Total Product Cost])/[Measures].[Sales Amount])*100 >
    (ParallelPeriod([DUE DATE].[Calendar Year],
      1, [DUE DATE].[Calendar Year]), (([Measures].[Sales Amount]-[Measures].[Total Product Cost])/[Measures].[Sales Amount])*100)
    Then 1
  When (([Measures].[Sales Amount]-[Measures].[Total Product Cost])/[Measures].[Sales Amount])*100 =
    (ParallelPeriod([DUE DATE].[Calendar Year],
      1, [DUE DATE].[Calendar Year]), (([Measures].[Sales Amount]-[Measures].[Total Product Cost])/[Measures].[Sales Amount])*100)
    Then 0