MDX calculated member total - mdx

Question

I'm using a calculated member for "previous period" as:
Case
// Test for current coordinate being on (All) member.
When [<<Target Dimension>>].[<<Target Hierarchy>>].CurrentMember.Level Is
[<<Target Dimension>>].[<<Target Hierarchy>>].[(All)]
Then "NA"
Else (
ParallelPeriod
(
[<<Target Dimension>>].[<<Target Hierarchy>>].[<<Target Level>>],
<<Number of Periods>>,
[<<Target Dimension>>].[<<Target Hierarchy>>].CurrentMember
),
[Measures].[<<Target Measure>>]
)
End
// This expression evaluates the difference between the value of the numeric
// expression in the previous period and that of the current period.
(snippet code taken directly from Microsoft suggestion)
It works as expected but when presenting the Totals I get the whole Year total, even if only some months are selected on rows.
So, if I select say year 2015, months Jan to Jun, I get the six correct values for 2014 months but a 2014 grand total instead of the sum of the six presented values.
Any way to get the "correct" sum value? By correct I mean the sum of the selected rows.
Edited to add the actual code:
Case
When [Dim Time].[Calendar].CurrentMember.Level Is [Dim Time].[Calendar].[(All)]
Then "NA"
Else (ParallelPeriod([Dim Time].[Calendar].[Year],
1,
[Dim Time].[Calendar].CurrentMember),[Measures].[Sales])
End
My Dim Time.Calendar has Year-Month-Day as levels. Easy enough :)
When selecting some months the Year total is the Grand total of the year, not the total of the selected months.
When selecting some days, the Month total is the Grand total of the month, not the total of the selected days.
Edited to add example:
Year Month Day Sales previous year Sales
2015 04 03 74,154.56 € 135,156.41 €
Total 04 2,617,045.75 € 135,156.41 €
Total 2015 37,696,665.69 € 135,156.41 €

Answer 1

(unsure if I should post an answer because it's not yet solved, but seems I found the right direction)
Using the suggestions here I defined a dynamic set (at cube definition time using MS SAS):
CREATE DYNAMIC SET CURRENTCUBE.[DynSet] AS [Dim Time].[Calendar]
and a Calculated member (on Excel, easier to test diferent syntax):
count([DynSet])
Now I get 1 as value on all rows, individual ones, subtotals, totals ... instead of the expected days of the selected month and the total sum.
Maybe someone with better MDX knowledge can develop it further.
I added also CM using the examples of the post count(descendants and count(existing( ... of the original [Dim Temps].[Calendar] and this is what I get:
Year Month Day Previous sales Sales CountExisting CountDescendants CountDays
2015 04 03 74,154.56 € 135,156.41 € 1 1 1
04 132,992.88 € 152,179.24 € 1 1 1
05 130,651.80 € 128,971.65 € 1 1 1
Total 04 2,617,045.75 € 416,307.30 € 31 31 1
Total 2015 37,696,665.69 € 416,307.30 € 365 365 1
I cannot understand how to use the new dynamic set as I'm not able to access its components, I expected [DynSet].[Year] [Month] and [Day] to exist so I could use them on my previous period expressions but they don't, so unsure on how to use it for my purpose.
Thks
Edited:
Tried to define
CREATE DYNAMIC SET CURRENTCUBE.[DynSet] AS [Dim Time].[Calendar].[Day]
and now my last column i.e. count([DynSet]) has a value of 3 for all lines.
Still no idea how to use [DynSet] levels ...

Answer 2

It took me almost two weeks, lots of searching hours and a dozen diferent forums, but finally I got a decent answer that solved the problem.
Take a look here
In brief, add a named calculation (not a calculated member) and scope the formula
SCOPE([Measures].[Previous_Sales]);
SCOPE([Dim Time].[Calendar].[Day].MEMBERS);
THIS = ([Measures].[Sales], ParallelPeriod([Dim Time].[Calendar].[Year])) ;
END SCOPE;
END SCOPE;
Simple enough once you know it!