Listen to a variable - is it possible?

Hey,
Im trying to set up an event listener that listens for when a variable has its data changed.

something like this:

var test = “testing…”;

test.addEventListener(variable.DataChangesInside, doSomething);

function doSomething(event:variable){
trace ("the new value in the variable is: " + event.target)
}

is there an event like that?

Thanks for any direction at all