MDX help in calculating Running total starting from immediate parent

Hi all,

I've the following MDX works and gives me a Running total from the highest level of the hierarchy to the current member. How in this I can make a change so that it gives me the running total starting from the immediate parent to the current member. For example, if I am returning all quarters of the year 2012, then the Running Total member should start from Q1 and give the Totals in the following way: Q1+0, Q1+Q2, Q1+Q2+Q3....

Thanks,

Guran

WITH MEMBER  [Measures].[Sales Cummulated]
AS
SUM(
    PERIODSTODATE
    (
        [Date].[Year-Quarter-Month-Week].[(All)],
        [Date].[Year-Quarter-Month-Week].CurrentMember
    ), [Measures].[Sales]
)

SELECT 
 {
[Measures].[Sales],
 [Measures].[Sales Cummulated] } on 0,
[Date].[Year-Quarter-Month-Week-Day].[Quarter].&[2012]&[1].Children on 1
FROM 
[Sales Cube]

GBM