balance forward of a supplier

Dear All,

is there any query to calculate the balance of the supplier from it's creation till sysdate other than the sum of the value of the below functions:

FUNCTION Pay_Function(frdate date,todate date) RETURN Number IS

TOT number :=0;

TOT_Pay_Rate number :=0;

seg3 character(50);

Ex_Rate_Inv number :=0;

Ex_Rate_Pay number :=0;

begin

    for C in 

    (select invpay.invoice_id inv_id,pay.currency_code invcurr,nvl(sum(invpay.amount),0)Amount, inv.accts_pay_code_combination_id acc_pay_code, pay.Exchange_rate ER

     from        apps.ap_checks_v pay,  apps.ap_invoice_payments invpay,apps.ap_invoices inv