<form NAME="javamsg">
経過秒数：<INPUT TYPE="text" NAME="time" SIZE="3">：
<INPUT TYPE="button" VALUE="STOP" onClick="clearTimeout(timer)">
<INPUT TYPE="button" VALUE="START" onClick="start()">
</form>

<SCRIPT LANGUAGE="JavaScript">
function init()
{
var now = new Date();
var tm   = Math.floor((now.getTime() - old.getTime())/1000);
tm  = ((tm < 10) ? "0" : "") + tm;
tm  = ((tm < 100) ? "0" : "") + tm;
document.javamsg.time.value  = tm
timer=setTimeout("init()",100)
}

function start()
{
old = new Date()
init ()
}
start()
</SCRIPT>