Hi Samuel,

I wanted to develop a measure that works with 2 differents ways : 

                        -      If the user filter a dimension1 then the Measure do something

                        -      If he doent use it then the measure will do something else.

And yes like you said, there is no function in MDX can detect if a dimension is used on filter or not. But I found a trick to do it :

I created a Measures Group  that contains 2 columns : The ID of the dimension that I want to detect and a boolean measure (0 or 1) , this table will contains all the ID of the dimension and the second column with 1 and 1 more line with ID = null and and the second columns = 0. Then I test if this measure = 0 (that means the dimension is not filtered) or  1( Dimension filtered)