Invoice Approval workflow generation to third person

Hi,

We are using AP invoice approval workflow. As of now worklow will get generated based on the HRMS (Requester -> Reporting manager).

We need to generate approval workflow to third person only for manual invoices based on the AP invoice amount.

Example -  A is raising invoice and approval workflow go to his manager B and he approve the invoice.

We need to generate the approval workflow for third person who is not related to A. Approval persons are same for all Manual invoices.

Invoice amount upto 5000- Work flow generated to person C ( Constant for all invoices)

Invoice amount upto  25000- Workflow should be generated to person D ( Constant for all invoices)