Just to clarify:
You're trying to make a section of your song loop indefinitely when you enter the section, until you give the command via MIDI to leave the section.
You're trying to make a section of your song loop only when you give the command via MIDI, the MIDI command triggering the section to loop once each time it is pressed. If no command is given, ALK will simply play right through that section and not loop it.
These are your two available options.
I've created a demo project which demonstrates both functions working:
Hope that clears things up!