iSupplier Portal - Replace the Field On the Portal

The iSupplier portal 'Account' tab gives an option to view the invoices and view the payments. There is a column PO Number which always gives us a blank or NULL value. In our setup we are saving the PO Number in the attribute3 field in the AP_INVOICES_ALL and want to replace that PO Field with attribute3.

Can someone suggest/guide us as to how we can go through the same. We have tried changing the view definition POA_AP_INVOICES_V but in vain. We also made the changes in  the XML file 'PosInvoicesVO.xml' but no luck.