var enableTimer = true;

function toggleTimer(btn, timerID) {
    enableTimer = !enableTimer;
    var timer = $find(timerID);
    if (enableTimer) {
        timer._startTimer();
        timer._raiseTick();
        btn.value = "Pause";
    }
    else {
        timer._stopTimer();
        btn.value = "Resume";
    }
}