updating totals passed onto paypal

Hi,
I am currently using OC v2.3.0.2 and I have modified the controller/confirm.php file to update the totals.
I have included some tax and weight based shipping cost and modified the totals accordingly.
I can confirm that the values are being saved correctly in the database and the values are displayed correctly in the checkout page, but it seems the new total items and do not appear in the paypal standard payment page. Could someone please give us a hint how to do this?
Thanks!
Ryan.