How to stop a while loop in a scheduled job

Hello,

I am using a while loop to vary the brightness of my unicorn pHat controled by a raspberry pi zero.

The job is scheduled (using the schedule module) to start at a certain time, but I don't know how to stop it. I have tried to schedule another job to off the LEDs but since schedule runs jobs in series, it never gets to the ending program.

Thanks for your help,
Charlotte