Master dimension will change if variable is changed

[Louis1]

Hi all,

i have created a master dimension with below expression:

=if(
(
((OpenDate<'$(vReportStartDate)' and isnull(CloseDate)) or (OpenDate<'$(vReportStartDate)' and CloseDate > '$(vReportEndDate)')) and
((OpenDate<'$(vCompareStartDate)' and isnull(CloseDate)) or (OpenDate<'$(vCompareStartDate)' and CloseDate > '$(vCompareEndDate)'))
),'Y','N')

if i selected 'Y' and then change the variables and select 'Y' again, it will show two selected field in selection bar.

How to fix it.

Best Regards,

Louis