Message flow into expanded event-based sub-process

Hi, can you please advice me?

I have two pools and in both of them I have expanded event-based sub-process with their content, where among others, I have intermediate message events (throw and catch).

Now I want to place message flow between two intermediate message events, while each of them is placed in other sub-process/pool.

Is it possible and if yes, how?

Modeler enables me only message flow ended on shape of sub-process, not message event inside sub-process.

Many thanks

Miroslav