1. sep-13 is the max(MonthYear) i.e the current month
2. Sep-12 is the max(MonthYear)-12 i.e same month last year
3. Mar-13 - Sep-13 is the last six MonthYear period
4. Mar-12 - Sep-12 is the last six months period for the last year.
what i wanna say is, the dimensions are calculated. i.e. all these four values will be coming from different expression but I want them to be displayed in a single header row.