Conditional Measure in Crosstab

[Marley]

Hi

I am trying to vary a query calculation being used in a crosstab as follows:

Measure Actual Plan Variance
Measure 1 x x x
Measure 2 x x x
Measure 3 x x y
Measure 4 x x x

I have a crosstab with a list of measures and their corresponding actuals, plan and variance (actual-plan) figures. The issue is that I would like the variance logic to change only for Measure 3 to be (actual-plan)*-1 so that a higher actual than plan is bad instead of good.

The current logic I have is below:
Tuple([Curr Month],[Actual])-Tuple([Curr Month],[Plan])

I have read about the CurrentMember function but am unsure how I would use it in this context. The measures are not part of a hierarchy but separate query calculations.

Any help would be much appreciated ;o)