asp中如何根据select的内容来显示或隐藏其他列表框

asp中怎么根据select的内容来显示或隐藏其他列表框
sel1的选项   1和2
当用户选择1的时候显示sel2，选择2的时候隐藏sel2

------解决方案--------------------
<script language=javascript>
if(form1.sel1.value= "1 ")
{form1.sel2.style.visibility=true}
else
{form1.sel2.style.visibility=false}
</script>

<form name= "form1 " ...>
<select name= "sel1 ">
<option value= "1 "> 1 </option>
<option value= "2 "> 2 </option>
</select>

<select name= "sel2 ">
<option value= "1 "> 1 </option>
<option value= "2 "> 2 </option>
</select>