asynchronous reading of the time slider position in PPRO

Dear ppro fellows,

I need to read out time slider position in a CEP panel every 50-100 milliseconds. This process should run in the background.

From what I collected  from the internet, I should add to my .jsx script function the following line:

setInterval(function() {
var CTI_ticks1 = app.project.activeSequence.getPlayerPosition().ticks;
alert(CTI_ticks1.toString());
}, 1000);

The thing doesn't work. Never produces alerts.

If a simply put:

var CTI_ticks1 = app.project.activeSequence.getPlayerPosition().ticks;
alert(CTI_ticks1.toString());

 the script works allright and the alerts are seen.

Could you recomment some solution on this?