variable change ... listener or watch

Hey,

I have a lot of dynamicly attached mcs.
They all have a function called init()

Here's the deal ...
In the root a variable called 'index' sometimes changes and when it does I want all the attached mcs to call the function init()

How do I accomplish this
//pod

initialize an event dispatcher.
add your mc's as listeners.
watch that variable for change.
if changed, dispatch event.