How to trigger a function when a variable changed?

How to trigger a function when a variable changed?

Hello,
We have a application for monitoring a key variable's changing and this variable has the int datatype.
When this variable's value changed, system should switched to the predefined screen. I try to do using the limit part for variable, but failed.:mad:
So how to realize this function? Thanks!

This is a migrated post! Originally posted on 16.05.2012 by user denver. Please be aware that information can be outdated.