So looking at the bit of the structure you pasted, at Holley and Hospital and ICU the names of the rooms? How do you handle multiple messages in a room? What structure is above this branch?
If those are the room names, and “rooms” is the top bucket, then something like this would populate your listviewer with the names of the rooms:
(you can ignore the timer block - leftovers from speed testing something else!)
That’s a basic example - you’ll want to do error checking and verify that value is not null before going on to set listviewer.