可输入内容的select

<form name="form1" method="post" action="">
<select name="c_cpu" style="position:absolute;width:150px;height:20px;clip:rect(0 180 110 130)" onchange='document.all.c_cpua.value=this.options[this.selectedIndex].value;'>   
<option value="1">1</option>   
<option value="2">2</option>   
<option value="3">3</option>   
<option value="4">4</option>   
</select>   
<input name="c_cpua" type="text" style="position:absolute;width:150px;height:20px">   
</form>