JS控制按钮10秒钟后才能正常使用~

script language="javascript">
function start()
{
    document.getElementById("Button1").disabled = true;
    document.getElementById("Button1").value = 10;
    window.setTimeout("tick()",1000);
    
}
function tick()
{
    var time = new Number(document.getElementById("Button1").value);
    if(time>0)
    {
        document.getElementById("Button1").value = time-1;
        window.setTimeout("tick()",1000);
    }
    else
    {
        document.getElementById("Button1").disabled = false;
        document.getElementById("Button1").value = "保存";
    }
}
</script>
<form >
<INPUT TYPE="button" NAME="Button1" id="Button1">
</form>

<script language=javascript>
 start();
</script>