Purchase approver per document type

ACaignie

Hello,
In the purchase approval setup I need to make a distinction between a purchase order and a purchase invoice.
Depending on the document type the approval request should be send to another user, regardless of who sends the request.
I have setup 2 workflows for this, but I can only assign one approver to a user.
Is there a way to change this without additional development? Or if with development, with an event subscriber?

We are using NAV2017 CU11.

Thx in advance
Andy