BiPublisher Sum within group Causing Error / Crash?

User_B5W17

I am utilising bipublisher with oracle intelligent advisor. I have the following group over 3 fields.

"Rate Card Item Description" "Quantity" "unitCostP3Final"

The grouping is working as is the summing on the quantity field, but when I try to sum the unitCostP3Final field, it is crashing. Quantity is mapped in, where as unitCostP3Final is calculated based on rules, not sure if this makes a difference. Please see below for code:

Existing code:

<?for-each-group:RCI;./RateCardItemsDescription_value?>

Field: Quantity [<?sum(current-group()/quantity_value)?> ]

Field: unitCostP3Final[<?sum(current-group()/unitCostP3Final_value)?>  ]

<?end for-each-group?>

Thanks