With the ticker and a counter, i think you can do your stuff:
var counter = 0;
createjs.Ticker.addEventListener("tick", handleTick);
var chronometer = ...
chronometer.cache(xChrono,yChrono,widthChrono,heightChrono);
function handleTick(event) {
// handle your drag and drop
// ...
if (counter == maxValue) { // maxValue = 1000 / createjs.Ticker.getInterval()
// redraw your chronometer
// ...
counter = 0;
chronometer.updateCache();
} else {
counter++;
}
stage.update();
}