Use Aggregate function to calculate a DIFFERENCE.

Question

I am trying to calculate a Forecast Variance "VR" from my Cube.  I have Daily Transaction and Forecast [Rec Type] (Record Types) coded "GL" (General Ledger or Sales), "FC" (Forecast) for all Products.  I created a
new MEMBER "VR" (Variance) as shown below.  This produces the SUM(Aggregate) of "GL" and "FC".  What I need is the DIFFERENCE.  I tried placing a (-1) in my formula.  It passed the syntax check but does not
produce any "VR" results.  Any suggestions would be appreciated.  Here is my Script View:
Thanks!
CALCULATE;                   
CREATE MEMBER CURRENTCUBE.[Measures].[SalesMTD]
 AS SUM(MTD([Dates].[Year -  Quarter -  Month -  Date].CurrentMember), [Measures].[Prime Qty]),
FORMAT_STRING = "#,##0;-#,##0",
NON_EMPTY_BEHAVIOR = { [Prime Qty] },
VISIBLE = 1 ,  ASSOCIATED_MEASURE_GROUP = 'PSI Activity';   
CREATE MEMBER CURRENTCUBE.[PSI Activity].[Rec Type].[All].[VR]
 AS Aggregate(
   ([PSI Activity].[Rec Type].[FC]),
   ([PSI Activity].[Rec Type].[GL])
  }, [Measures].CurrentMember
FORMAT_STRING = "#,##0;-#,##0",
NON_EMPTY_BEHAVIOR = { [Prime Qty] },
VISIBLE = 1 ,  ASSOCIATED_MEASURE_GROUP = 'PSI Activity'  ;
Mario

Answer 1

TRy the below query.Wont it give the expected result?
CREATE MEMBER CURRENTCUBE.[PSI Activity].[Rec Type].[All].[VR]
 AS (
   ([PSI Activity].[Rec Type].[FC],[Measures].CurrentMember)-
   ([PSI Activity].[Rec Type].[GL],[Measures].CurrentMember)
FORMAT_STRING = "#,##0;-#,##0", 
NON_EMPTY_BEHAVIOR = { [Prime Qty] }, 
VISIBLE = 1 ,  ASSOCIATED_MEASURE_GROUP = 'PSI Activity'  ;