Sum of quantity field without declaring it a flow field.

Sir,

I've created a field named 'Quantity Available' in MR Subform page which will sum up all the quantityes available in the 'Quantity' field of the Item Ledger Entry table.I didn't declare the field as a flowfield. I wrote the following code in MR Subform page:

Quantity Available - OnValidate()

RecILE.SETCURRENTKEY(RecILE."Location Code");

RecILE.CALCSUMS(RecILE.Quantity);

But still doesn't get the required result. What should I do?

Thank You,