一页中有两个下拉框，如果右边的框里出现了这个数，左边就不显示怎么写！

代码大概如下：

1<form action="te.jsp" method="post" name="choiceForm">   
2。。。   
3<select multiple="" name="nodeData" size="30">//左边的框

for(int j=0;j<netnode.getrecordcount();j++) <option="" ="" nodedata="(cEquipObject)netNode.GetRecord(j);" {=""> = nodeData.Ip_address

}

1</netnode.getrecordcount();j++)></select>
2<select multiple="" name="choiceBox" size="30" style="width:175;">```
3   
4for(int j=0;j&lt;info.getrecordcount();j++) &lt;option="" ```="" data14="(cAlarm_Operator)Info.GetRecord(j);" {=""> ```
5=data14.strIp_address
6```//右边的框

}

 1</info.getrecordcount();j++)></select>   
 2\---------------------------------------------------------------   
 3  
 4看看这个   
 5  
 6<html>
 7<head>
 8<title></title>
 9</head>
10<body marginheight="0" topmargin="0">
11<table align="center" border="0" height="132" width="100%">
12<tr>
13<td height="80">
14<div align="center">
15<form action="ckmain.asp" method="post" name="form2" target="mainFrame">
16<table align="center" border="0" cellpadding="0" cellspacing="0" class="table2" width="770">
17<tr bgcolor="#99CCFF" class="tbale1">
18<td bgcolor="#CAE7F7" class="tbale1" colspan="6" height="28"> <label>
19</label>
20<div align="center">
21<label> ÇëÑ¡Ôñ²éÑ¯Ìõ¼þ   
22<select id="select" name="fhd" onchange="aa(this)">
23<option value="1">a</option>
24<option value="2">b</option>
25</select>
26<select id="retor" name="retor">
27</select>
28<input id="textfield" name="textfield" style="visibility:hidden" type="text"/>
29</label>
30</div></td>
31</tr>
32<tr bgcolor="#99CCFF" class="table1">
33<td bgcolor="#CAE7F7" class="tbale1" width="183"> </td>
34<td align="center" bgcolor="#CAE7F7" class="tbale1" colspan="2" valign="middle">
35<input name="Submit" type="submit" value="¿ªÊ¼²éÑ¯"/>   </td>
36<td align="center" bgcolor="#CAE7F7" class="tbale1" valign="middle"> </td>
37</tr>
38</table>
39</form>
40</div></td>
41</tr>
42</table>
43<script>   
44function aa(oE)   
45{   
46var oA = document.all("retor");   
47var oB = document.all("textfield");   
48if(oE.options[oE.selectedIndex].text == 'a')   
49{   
50oA.style.visibility = "";   
51oB.style.visibility = "hidden";   
52}   
53else   
54{   
55oA.style.visibility = "hidden";   
56oB.style.visibility = "";   
57}   
58}   
59</script>
60</body>
61</html>   
62  
63\---------------------------------------------------------------   
64  
65<span style="display:''">   
66  
67if右边的框出现了这个数，   
68  
69左边display=none</span></form>