Except
Evaluates two sets and removes any tuples from the first set that also appear in the second. You can optionally specify to retain duplicates.
Syntax
Except(Set_Expression1, Set_Expression2 [, ALL ] )
Input parameters
Set_Expression1
An MDX expression that returns a set. This must consist of tuple sets from the same hierarchy as Set_Expression2.
Set_Expression2
An MDX expression that returns a set. This must consist of tuple sets from the same hierarchy as Set_Expression1.
ALL
If specified, the function retains duplicates found in the first set; any found in the second are still removed. The members are returned in the order in which they appear in the first set.
Example
Except( [DateCustom].[StandardMonth].CurrentMember.Siblings, [DateCustom].[StandardMonth].CurrentMember.Lag(1).Siblings )