Assuming you want a sound file to play when each break starts:
- Create a new Event, select "Create a new event from scratch"
- Trigger: "A level starts"
- Conditions: "isBreak and breakNum=1"
- Add an Action to the event to play the sound file for the first break
Repeat, changing the Conditions to "isBreak and breakNum=2" and "isBreak and breakNum=3" for the second and third breaks, respectively.