Asynchronous call between external system and SAP CRM

Hi,

I am trying to make an asyncrhronous call between an external system and SAP CRM.

This is the scenario:

1. SAP CRM through ODI sends a request to a webservice in an external system (using a proxy class).

2. This external system will be able to send asynchronous responses (associated to the request) to SAP CRM ODI (responses can be sent to SAP CRM ODI after, e.g. 1 minute, 1 day, ...)

Is there in SAP CRM ODI any way to handle step 2 of my process? I would like to know how CRM knows that a response is comming back and how to execute some code associated to the response.

Thanks a lot for your help.