这个JS哪里错了？

[zhaolinlong]

我是想检验一个下拉列表的值，可为什么错呢？我的代码如下:

<script language="JavaScript">
function show()
{
if(form1.select1.disabled==true)
form1.select2.disabled=true;
else
form1.select2.disabled=false;
}
show();
</script>
<form name="form1" method="post" action="">
<table width="163" border="1">
<tr>
<td width="45">name</td>
<td width="102">

<select name="select1" disabled>
<option>wo</option>
<option>ni</option>
</select>

</td>
</tr>
<tr>
<td>sex </td>
<td>

<select name="select2">
<option>男</option>
<option>女</option>
</select>

</td>
</tr>
<tr>
<td colspan="2"><div align="center">
<input type="submit" name="Submit" value="提交">
</div></td>
</tr>
</table>
</form>

运行说form1.select1为空或不是对象，真不明白！

[lfecnu]

把
<script language="JavaScript">
function show()
{
if(form1.select1.disabled==true)
form1.select2.disabled=true;
else
form1.select2.disabled=false;
}
show();
</script>
写道最后