How to mass update accrual account in POs

Summary:

Mapping sets are revised for accounts. New PO's follow the new mappings correctly, but existing PO's have old values. We're already aware that we can manually rebuild the accounts to populate correct values, but it's lot of manual action to perform for hundreds of PO's. Is there a way to mass update the values?

Content (required):

1. We setup the expense accrual account 20021 in mapping set.

2. After go live for a while, the client want to change the accrual account to 20027.

3. We change the setup and the newly created PO will have the new accrual account.

4. However, we still have the old account 20021 for existing PO. I know that I can rebuild the account in distribution level one by one.