Hi Praveen,
As said by Amit , you can do sum in Excel within Xcelsius, Map pin (e.g. A1:A50) and Debit(B1:B50) to Excel columns which are coming from WSDL and in next Excel column apply formula for sum.
PIN = SUM (pin( col.A) + Debit(Col. B).
Map this PIN column to one of your chart series.
Regards,
Avinash