Orchestrator Association Not working with Form Exit Event

Hello Experts,

I am trying to call an orchestrator using from an E1 application using Orchestrator Association Functionality so that we can avoid customization but unable to do so.

Request you to please let me know if what I am trying is possible.

Use Case -

Business requirement is Once Purchase Order is fully approved (P43081) system should be able to trigger an Notification to Supply Administrator to perform compliance check on the Purchase Order & release it (P43070).

We have built an orchestrator which can validate if an Purchase Order is fully approved and then trigger an notification email however the problem is we are unable to call it from P43081 Form Exit 'Approve event'