MDX - how to calculate the sales between a certain period and the currentmember with a max date

Question

Hi all,
1)I need to calculate the sales between W1 and the currentmember, but the max date should be W20. How can I solve this in MDX?
MEMBER [Measures].[Q1 act.period to date sales] AS
Sum(
[Date invoice].[Bonus calendar - Week].[Bonus week of year].&[2015]&[1]
[Date invoice].[Bonus calendar - Week].Currentmember
*[CurrentSalesPeriod]
,[Measures].[Sales amount]
This is the measure I have, I need to add the max date is W20. 
2)Also, when I calculate the sales between [Date invoice].[Bonus calendar - Week].[Bonus week of year].&[2015]&[40] and the currentmember, for example being [Date invoice].[Bonus calendar - Week].[Bonus week of year].&[2015]&[20],
he calculated the sales between this period. However, in theory this is not possible because W20 < 40. Is there any way I can put a constraint on this that he only calculates the sales if the currentmember is > the start period?
Thanks in advance!

Answer 1

Y, you can put a check on to determine if currentmember > start period.
Firstly, your period keys are composite of year and period (indicated by the two ampersands in the fully qualified date above). If your period keys were non-composite (eg 201501) it would be a simple matter of 
IIF([Date invoice].[Bonus calendar - Week].Currentmember.properties("key") > [Date
invoice].[Bonus calendar - Week].[Bonus week of year].&[2015]&[1].properties("key"),[Measures].[Sales
amount],null)
There are advantages of having two period attributes on the dimension, one with a fully unique
key and the other with just the period of fy, but that's digressing.
With your composite keys, you could use a calc like the following for the SUM()
Sum(
[Date invoice].[Bonus calendar - Week].[Bonus week of year].&[2015]&[1]
[Date invoice].[Bonus calendar - Week].Currentmember
*[CurrentSalesPeriod]
,IIF([Date
invoice].[Bonus calendar - Week].Currentmember.parent.properties("key") +[Date
invoice].[Bonus calendar - Week].Currentmember.properties("key") > [Date
invoice].[Bonus calendar - Week].[Bonus week of year].&[2015]&[1].parent.properties("key")+[Date
invoice].[Bonus calendar - Week].[Bonus week of year].&[2015]&[1].properties("key"),[Measures].[Sales
amount],null))
Richard