Calculating a % rate based on two date dimension in one cube - sql-server

Question

Set up - SSAS 2012 with OLAP cubes (built by supplier) and MS Report Builder v3. No access to BIDS.
I am building a report which needs to calculate a disposal rate based on data from a single cube. Historically this would have been calculated from two separate tables of data, giving a count by month of new items by date recorded and a count by month of items disposed by month of disposal. This can then be turned to a disposal rate using a lookup or similar.
Blank disposal dates are fine (can take months to dispose of items).
I would like to keep this in a single query so that I can introduce extra dimensions to analyse the data and represent it multiple ways easily. My suspicion is that I need a calculated member but I am not sure where to start with these. Any help would be greatly received - I am trying out a few things and will update this should I solve myself.
Simple formula would be
=(sumif(Items, DateReported="July 2014"))/(sumif(Items, Disposal Date="July 2014"))`
So the following data...
Month Recorded Month Disposed No of Items
May-14 May-14 25
May-14 Jun-14 3
May-14 Jul-14 45
Jun-14 232
Jun-14 Jun-14 40
Jun-14 Jul-14 46
Should produce...
Month No Recorded No Disposed Disposal Rate
01/05/2014 73 25 34%
01/06/2014 48 43 90%
01/07/2014 45 91 202%
My current MDX statement:
SELECT
NON EMPTY { [Measures].[No of Items] } ON COLUMNS,
NON EMPTY
{
([Date Reported].[Calendar Months].[Month].ALLMEMBERS
*
[Disposal Date].[Calendar Months].[Month].ALLMEMBERS )
} ON ROWS
FROM [Items]

Answer 1

You can use LinkMember to move a reference to one hierarchy (like [Date Reported].[Calendar Months]) to another one (like [Disposal Date].[Calendar Months]), provided both hierarchies have the exact same structure. Thus, only using [Date Reported] in your query, the calculation can use [Disposal Date]. The query would be like the following:
WITH MEMBER Measures.[Disposed in Date Reported] AS
(Measures.[No of Items],
LinkMember([Date Reported].[Calendar Months].CurrentMember, [Disposal Date].[Calendar Months]),
[Date Reported].[Calendar Months].[All]
)
MEMBER Measures.[Disposal Rate] AS
IIf([Measures].[No of Items] <> 0,
Measures.[Disposed in Date Reported] / [Measures].[No of Items],
NULL
), FORMAT_STRING = '0%'
SELECT { [Measures].[No of Items], Measures.[Disposed in Date Reported], Measures.[Disposal Rate] }
ON COLUMNS,
[Date Reported].[Calendar Months].[Month].ALLMEMBERS
ON ROWS
FROM [Items]
Possibly, you would want to adapt the column titles in your report. I left that out and used member names that desribe more what they do than what should be shown to users.