Opening balance in report

Hi
I am create a report of general ledger printing,Problem is-
if i take a report from 01/04/05 than report show
the properly and opening balance show in each a/c head.
But if i want to take a report from 01/05/05 than
opening balance of 01/04/05 is show in a/c head but i want
opeining balance should be calcutaed as on 01/05/05 and shown.

Please guide how the report will generate the as on date opening
balance -

I am attaching herewith the query & report file

query
-----
SELECT PARTY.PARTYNAME AS PARTYNAME, GEN.GLNAME AS GLNAME,
GEN.AMOUNT AS OAMOUNT, CASH.CASHNAME AS CASHNAME,
GEN.CB AS CB, TXN.GLCODE AS GLCODE, TXN.VOUCHER AS VOUCHER,
TXN.DOCDATE AS DOCDATE, TXN.AMOUNT AS TAMOUNT, TXN.VTYPE AS VTYPE,
TXN.NARR AS NARR, TXN.CHEQUE AS CHEQUE, TXN.CHEQDATE AS CHEQDATE,
TXN.BANK AS BANK, TXN.BILLNO AS BILLNO, TXN.BILLDT AS BILLDT
FROM PARTY RIGHT JOIN
(GEN RIGHT JOIN (TXN LEFT JOIN CASH ON TXN.CBCODE=CASH.CBCODE)
ON GEN.GLCODE=TXN.GLCODE) ON PARTY.PARTYCODE=TXN.PARTYCODE
WHERE GEN.GLCODE NOT IN (SELECT CASHCODE FROM CASH);

--> In this query oamount hold the opening balance of 01/04/05 and
tamount is the daily transaction amount.