function onSourceDownloadProgressChanged(sender, eventArgs) {
    if (sender.findname("_Text") != null) {
        sender.findName("_Text").Text = (Math.round(eventArgs.progress * 100)) + "%";
    }
    if (sender.findname("progressBar") != null && sender.findName("progressBarBackground") != null) {
        sender.findName("progressBar").Width = eventArgs.progress * sender.findName("progressBarBackground").Width;
    }
}