Rolling 12 months in Webi 3.x

Hi Experts,

I am trying to create a report in WEBI Where I have 3 columns

1)Date

2)Amount

3)12 months rolling amount

Date object I have formatted it in the universe to get the MON-YYYY, So that I can the data by months, And its working correctly.

In the report I am getting data like this.

Date      Amount     

Jan-2008     5000

Feb-2008     6000

Mar-2008     8700

Apr-2008     5500

I want another column for 12 month rolling amount which show the data from for last one year.

example : Jan-2008 for 12MonthRolling Amount column I should get the total of Jan-2007 to Dec-2007

          Feb-2008 for 12MonthRolling Amount column I should get the total of Feb-2007 to Feb-2007

User will be having the prompt to select the end Date

I have created the Measure for 12 month rolling amount to select the last 12 month total based upon the prompt.

Please suggest me if you get any idea on this requirement.

Its very urgent...

Thanks in Advance,

sowjanya k.