Solved Send file with Join that has %VARIABLE in its name

Hi all. I'm setting up an old tablet to act as a hub for my home devices.

Till now, I managed to do this: I send a request from my phone with Join, then Tasker on my tablet fetches the request, and starts a task that creates a log.txt file with some infos that I need (like %BATT, %UPS, and so on).

The point is: I want to send this log back to my phone. I set that every log request should create a log file, whose name is

log%FILENAME.txt

having set %FILENAME as %TIMES_%DATE, so that every time it creates a new log with a new name.

How can I then send this specific file I've just created with Join? When I create a Join task, it just asks for a file to choose and doesn't allow me to put variables in that field.