[K12OSN] OT: what do you use to schedule you schools bells

[Timothy C Litwiller]

I need to find something "free" or very low cost to run the bells at our 
28 student private school. I think I have found a relay switch that I 
can control with usb and wire into the bell circuit along with the the 
push button.

But I need some software that the teachers can use to schedule.   I can 
setup the default - but some times things get changed around for a few 
days and I don't want to have to be there for every change.