Put RFC feedbcak which happened in inbound messagemapping into outbound message

Hi experts.

I am trying to add a customized authority check in PI system, request message will go into receiver system as expect only if authority check passed.

Now I am doing as:

1. create a RFC in ABAP client containing the customized authority check logic, and RFC will return 'S' for success, 'E' for error

2. use the RFC in inbound message mapping as a RFC lookup

3. only when RFC loopup get 'S', then the request message will go into receiver system as expect;

if RFC lookup get 'E', I want to the processing stopped and put a special message into outbound message as a feedback to sender system.

Just liks this pic:

if RFC get 'S', sender system will get a expected feedback message which was generated by Receiver System;

if RFC lookup get 'E', the messge will not go futher into receiver system, and sender system will get a sepcial feedbcak message which was gernrated by PI system,

the message maybe like: { "RETURN": { "MessageType": "E", "MessageText": "Authority check failed" } }

Now I don't know how to achieve this when RFC get 'E'.

Pls help me out.