Defining a calculated member in MDX - filtering a measure's value

Answer 1

To begin with, you can define a new calculated measure in your MDX, and tell it to use the value of another measure, but with a filter applied:

WITH MEMBER [Measures].[Incoming Traffic] AS
'([Measures].[Total traffic], [Direction].[(All)].[In])'

Whenever you show the new measure on a report, it will behave as if it has a filter of 'Direction > In' on it, regardless of whether the Direction dimension is used at all.

But in your case, you WANT the Direction dimension to take precendence when used....so things get a little messy. You will have to detect if this dimension is in use, and act accordingly:

WITH MEMBER [Measures].[Incoming Traffic] AS
'IIF([Direction].currentMember = [Direction].[(All)].[Out],
    ([Measures].[Total traffic]),
    ([Measures].[Total traffic], [Directon].[(All)].[In])
)'

To see if the Dimension is in use, we check if the current cell is using OUT. If so we can return Total Traffic as it is. If not, we can tell it to use IN in our tuple.