Action If A Variable Changes?

Maybe this is not possible, I'm stuck on finding a method that would allow this to work. I know I can script checking for a specific variable change like this:

If ($WhatIsForDinner = "ChickenPotPie")
Print("Yummy")
EndIf

But I would like a script to take action anytime a specific variable changes. This would just run all the time looping and looking for a change to the variable in order to take action. Does anyone think that is possible?

:ChangeDetected
If ($WhatIsForDinner = *Changed?)
DoSomething
EndIf
GOTO(ChangeDetected)