Cumulative measure without date hierarchy - ssas

Question

I've not much experience with multidimensional cubes, SQL and Tabular modeling are more my thing.
I'm trying to create a calculated measure that's a running total across time periods (months). The trouble is, I'm not using a traditional date dimension because this "Period" dimension has an "Opening balance" category. This is a requirement set by the customer.
The [Dim Period] table is pretty simple, it has a key which is starts at 201800 and goes through to 201812. 201800 being the opening period. I've tried to create a simple hierarchy, though there are no attributes lower than the Period.
So far I've come up with this;
WITH MEMBER [Measures].[YTD Total] AS
Aggregate
(
PeriodsToDate
(
[Dim Period].[Period Hierarchy].[Period],
[Dim Period].[Period Hierarchy].CurrentMember
),
[Measures].[Total]
)
SELECT
{[Measures].[Total], [Measures].[YTD Total]} ON COLUMNS,
{[Dim Period].[Period Hierarchy].[Period]} ON ROWS
FROM
[My Cube]
This returns the same value in the [Total] and [YTD Total] column, so I'm obviously doing something wrong.
For reference, here's a measure I created in a Tabular model that does work;
YTD Total:=CALCULATE([Total],FILTER(ALL(DimPeriod[Period]),DimPeriod[Period]<=MAX(DimPeriod[Period])))
Any pointers would be greatly received.

Answer 1

I think I've found the answer;
WITH MEMBER [Measures].[YTD Total] AS
Aggregate
(
PeriodsToDate
(
[Dim Period].[Period Hierarchy].[(All)],
[Dim Period].[Period Hierarchy].CurrentMember
),
[Measures].[Total]
)
SELECT
{[Measures].[Total], [Measures].[YTD Total]} ON COLUMNS,
{[Dim Period].[Period Hierarchy].[Period]} ON ROWS
FROM
[My Cube]