Yes - as long as the drill path uses fields, rather than calculated dimensions. Use GetCurrentField('drillGroupName') to get the current level of the drill down. Use this in your expression, like this:
=if(GetCurrentField('group') = 'Month', <expression for month>, <expression for other>)
In QV, the editor falsely flags this as an error -- I am not sure if the QS editor has the same flaw.
Logic will get you from a to b. Imagination will take you everywhere. - A Einstein
Yes you can change the measure when using drill-down dimension but we have to mention what are he measure to be calculated in expression better use a set analysis for it
