On a PO matched manual invoice, whenever if any new lines added that should go for approval

We have a requirement from our business that on a PO matched Manual Invoices , if anyone of the users adds new Line/Lines then that should go for approval. It should follow approval process. Can i know the rules condition or attributes to be added to meet the requirement from Invoice Lines ?

Note -

1) Currently in the system, the rule is set such that PO matched manual invoices are going for Auto-approve. This rule is to be continued.

2) Requirement is that if any additional lines the user adds to that invoices then that should follow a approval process and the approver can be supervisory or approval group based on requirement.