How to calculate the previous year YTD balance in profit & loss statement

Dear all,

I would like to seek for advice on how to calculate the previous year YTD (Year to date) balance in profit & loss statement

For example, if I enter May 2009, the YTD value should be a sum up of value from Jan to May.

I have tried the current year YTD could be set in column selection dimension "financial period"

FACT PER( Code = YearFirst(@Per):@Per ) Order By PER.Code Descending

Then, I tried the previous year YTD in another column using

FACT PER( Code = YearFirst(@Per-12):@Per-12 ) Order By PER.Code Descending

But it failed -> Abnormally display three column, while the financial period I enter 200903 in parameter @Per

Would anyone kindly help me on that?

Regards,

Simon Chiu