Hello,

Thank you for your link and your help.

But, I have found this link that corresponds more to my issue :

http://social.msdn.microsoft.com/Forums/sqlserver/en-US/d2f822a5-2a7a-4ec5-9db4-35a107d8fcb9/mdx-parallelperiod-month-to-month

Here is my MDX request if it can help :

SUM(Generate(Existing {[Time].[Date].Children},

{PARALLELPERIOD([Time].[Year - Month - Date].[Year]

,1

,OPENINGPERIOD([Time].[Year - Month - Date].[Date],[Time].[Year - Month - Date].CurrentMember))

:

PARALLELPERIOD([Time].[Year - Month - Date].[Year]

,1

,TAIL(DESCENDANTS([Time].[Year - Month - Date].CurrentMember,[Time].[Year - Month - Date].[Date],LEAVES)

,1).Item(0))

})

,[Measures].[Nb Jour Ouvré]

)