AP Invoice Workbench Personalization

Hello,

I have a client who is currently divesting one of their business units. As a result, the historical data will remain in the original company's instance. I have a requirement to prevent AP Invoice Entry processors from being able to modify any invoices or payments for the company (balancing segments) being divested. Has anyone ever done a forms personalization in the AP Invoice Workbench or Quick Payments forms to prevent a transaction from being able to be updated based on the balancing segment?

Scenario:

I have AP Invoice Entry for company 1 and company 2. Company 1 sold company 2. A new instance is being created for company 2; however company 1 will retain historical data. We need to be able to prevent users with Invoice Entry from being able to update any historical AP Invoices or Supplier Payments only for company 2.