Rollup on Dynamic Subset

[anthony.mower]

Hi All

I have a time dimension that has 4 levels Total, Year, Month, Week End Date.  I have created a Dynamic Subset on this dimension which uses a parameter cube in order to get the week end dates for the current year as per below.

Except({Filter({TM1SUBSETALL([Time_Week_End_Dim])},[Time_Week_End_Dim].[D_ID Serial] >= [Lk - Parameters].([Parameter].[Start of Year D ID], [General Measures].[Amount]))},
{Filter({TM1SUBSETALL([Time_Week_End_Dim])},[Time_Week_End_Dim].[D_ID Serial] >= [Lk - Parameters].([Parameter].[Current Week End D ID], [General Measures].[Amount]))})

What I need to do however, is to roll up these dates in order to just display a single line on the active form for the year to date sales