程序代码：

<script language="javascript">
function overFocus(ob1,ob2){if(ob1.value.length==2){ob2.focus();if(ob2.value!=""){ob2.value="";}}}
</script>
<form name="form1">
<div><input type="text" name="R1" onkeypress="overFocus(this,document.form1.R2)" /></div>
<div><input type="text" name="R2" onkeypress="overFocus(this,document.form1.R3)" /></div>
<div><input type="text" name="R3" onkeypress="overFocus(this,document.form1.R4)" /></div>
<div><input type="text" name="R4" onkeypress="overFocus(this,document.form1.R5)" /></div>
<div><input type="text" name="R5" onkeypress="overFocus(this,document.form1.R6)" /></div>
<div><input type="text" name="R6" onkeypress="overFocus(this,document.form1.R7)" /></div>
<div><input type="text" name="R7" onkeypress="overFocus(this,document.form1.R8)" /></div>
<div><input type="text" name="R8" onkeypress="overFocus(this,document.form1.R9)" /></div>
<div><input type="text" name="R9" onkeypress="overFocus(this,document.form1.R1)" /></div>
</form>