===========请教：如何实现Input(text类型)框中部分value的选中===========

<HTML>
<HEAD>
</HEAD>
<BODY>
<FORM NAME="formName">
<INPUT TYPE="text" 
       NAME="date" 
       VALUE="YYYY-MM-DD"
       SIZE="10" STYLE="font-family: 'Courier New';"
       ONFOCUS="this.select(); 
                this.oldValue = this.value;"
       ONKEYUP="var n = this.value.length;
                this.value = this.value + this.oldValue.substring(n);
                var range = this.createTextRange();
                range.moveStart('character', n);
                range.select();
                this.oldValue = this.value;"
>
</FORM>
</BODY>
</HTML>