How to make PO Charge Account field non-updateable when 2-Way matched PO's matched to an Invoice

When Purchase Order with 2-way match is matched to an Invoice, users are still able to update the PO Charge Account on PO from PO Distribution Tab. This create mismatch between PO and AP charge account, if the change on PO is done after the Match. Kindly suggest any workaround to prevent this issue. Thanks, Chetan