Crosstab Custom Calculation calculation in RTF template

 Hi,

  I am creating Pivot table by Using RTF template, I want do some extra calculation in the Aggregation Part.

  Code of My Pivot Table is show below:

   ?crosstab:c12918;"//G_1";"SUPPLIER_NAME{,o=a,t=t}";"BUSINESSMONTH{,o=a,t=t}";"QTY";"sum"?>

    The result of Pivot is :

                                        November October

     AUS Warehouse         26               10

      Local Grocery             0                 41   

Now, what I want to do custom calculation like this  Sum(Qty)/720*100 

I would be really grateful, if anyone advise me.