DATESUBDATE(now(), B3, "d") + "天" + mod(DATESUBDATE(now(), B3, "h"), 24) + "小时" + mod(DATESUBDATE(now(), B3, "m"), 60)+ "分钟" + mod(DATESUBDATE(now(), B3, "s"), 60) + "秒" 时间差 天时分秒格式
这样的效果?

在WEB属性里 填报预览 加载结束事件里写 这个JS
//每秒执行一次
setInterval(function() {
//将当前时间赋值给M
var M = FR.remoteEvaluate('=DATESUBDATE(now(), "2019-10-28", "d") + "天" + mod(DATESUBDATE(now(), "2019-10-28", "h"), 24) + "小时" + mod(DATESUBDATE(now(), "2019-10-28", "m"), 60) + "分钟" + mod(DATESUBDATE(now(), "2019-10-28", "s"), 60) + "秒"');
//给C4单元格赋值M
contentPane.setCellValue("C1", null, M);
}, 1000);