Sender Proxy - Multiple Message problem

Hello,

I have a problem in a proxy process. I have a Sender Proxy which reads a file and sends it to PI. The file is converted into IDocs and sent to SAP ERP. The problem is that my mapping is splitting the file and sending multiple IDocs. So in my mapping I have Split template.

To the messages default the Messages and Message tags are added. The problem is when I sent my message from Proxy I am not able to add these Messages and Message tags.

Is there a way to add it? Or is it not possible?

Thanks.