Finding related date to Calculated Measure in MDX - mdx

Question

BackStory
I am working in MDX and my measure groups use many calculations. Many of these are timeframes such as [Date].[Fiscal].[LY WTD] which stands for last year week to date.
To calculate this I was using the ParellelPeriods function. However as our calendar has 52 weeks for one year and 53 for the current year my calculations are off.
I have made my changes using
CREATE MEMBER CURRENTCUBE.[Date].[Fiscal].[LY WTD] as
Aggregate(
Exists(
[Date].[Date].[Date].members,
{
[Date].[F Day Of Week].[F Day Of Week].item(0) :
Exists([Date].[F Day Of Week].[F Day Of Week].members, [Date].[Last Complete Day].&[Y]).item(0)
}
* Exists([Date].[F Year].[F Year].members,[Date].[Last Complete Day].&[Y]).item(0).lag(1)
* Exists([Date].[F Week of Year].[F Week of Year].members, [Date].[Current Week].&[Current Week])
)
), VISIBLE = 0;
I now need to test this.
Problem
How can I determine what week my measure [Date].[Fiscal].[LY WTD] is pulling back?

Answer 1

Could you add a test member like this?
CREATE
MEMBER CURRENTCUBE.[Date].[Fiscal].[LY WTD - Caption] AS
Exists
(
[Date].[F Week of Year].[F Week of Year].MEMBERS
,
{
[Date].[F Day Of Week].[F Day Of Week].Item(0)
:
Exists
(
[Date].[F Day Of Week].[F Day Of Week].MEMBERS
,[Date].[Last Complete Day].&[Y]
).Item(0)
}*
Exists
(
[Date].[F Year].[F Year].MEMBERS
,[Date].[Last Complete Day].&[Y]
).Item(0).Lag(1)*
Exists
(
[Date].[F Week of Year].[F Week of Year].MEMBERS
,[Date].[Current Week].&[Current Week]
)
).Item(0).Item(0).Member_Caption
,VISIBLE = 1 ;

Answer 2

I think my problem is that as I am aggregating my calc script it is impossible to then see the individual original members. Here is what I ended up doing.
1. First I used the same script that I was using to make my calculation in a mdx query and ensured I got the dates I expected.
Select
{Measures.[Gross Units]} on 0,
Exists(
[Date].[Date].[Date].members,
{
[Date].[F Day Of Week].[F Day Of Week].item(0) :
Exists([Date].[F Day Of Week].[F Day Of Week].members, [Date].[Last Complete Day].&[Y]).item(0)
}
* Exists([Date].[F Year].[F Year].members,[Date].[Last Complete Day].&[Y]).item(0).lag(1)
* Exists([Date].[F Day of Year].[F Day of Year].members, [Date].[Current Week].&[Current Week])
)
on 1
From myips
Results:
Gross Units 2015/05/09 (null) 2015/05/10 13,069 2015/05/11 35,853
2015/05/12 104,617 2015/05/13 46,318
2. Then I looked for the results, using my calculation for last year week to date and comparing that to a query scoped calculated member aggregated of those days
With Member [Date].[Fiscal].[Custom] as
Aggregate([Date].[Fiscal].[Date].&[2015-05-09T00:00:00]:[Date].[Fiscal].[Date].&[2015-05-13T00:00:00])
Select
[Date].[Fiscal].[Custom]
//Date.Fiscal.[LY WTD]
on 0,
Measures.[Gross Units]
on 1
From myIPS
**I got the same results! Success!**