Why can't you receive the system property's more than once in flash?

Hello,

I have something very simple.

function traceHeight() {

trace(System.capabilities.screenResolutionY);

}

setInterval(traceHeight, 1000);


During the movie when you switch to another resolution the value keeps the same.
But when you restart (publish) your movie again the right value comes up.

Does that mean it is not possible to receive the system properties in real time??