Sales Order Approval additional steps after rejection

Summary:

For our customer we have the following sales order approval business scenario:

All the sales order are created through integration using a generic integration user, there is no manual capture of sales orders

Planning want to approve and reject a sales order based on a flag on the order line

I have setup the approval rule based on the value of the flag and the approval gets triggered and sent to the planner. This is all working fine

The requirement they have is that if the planner rejects the sales order that a notification is sent to the customer service team with planner comments so they can update the sales order.