Would like audio to play, but cycle through 3 separate tracks.

I have successfully created a canvas with a "start" button which on tap starts audio and timer, then button label changes to "stop" and tapping it then stops audio and timer. The audio is a meditation track of spoken words. My problem is, and the part I haven't been able to accomplish yet, is that I want a different track to play each time - I have 3, and I just want the app to cycle through each one at a time (cycle through next one to play on load of the page).

I guess my question is, is this even possible or am I better off using bare minimum 1 audio track and get the thing into the app store to test traction before I pay my developer to build it. If I'm trying to do something impossible with FlutterFlow as a no-code option, I'd rather find out sooner than later. Thank you in anticipation!

Audio player widget seems to be no good as it doesn't want to be controlled by a separate button. Can't seem to do it via "play sound" action because when I have nested conditionals each "playsound" action is called the same thing and I can't rename them manually - flutterflow doesn't like it. I'm now trying to use custom code to control audio and have created an "on page load" action to update integer associated with 3 tracks I've labelled with the 3 integers and loaded as files into a Firestore collection and using a backend query to update app state to recall the correct file. Can't test if it's going to work as I get the attached error. I have tried setting a default track, so it has a value to start with....