问题： ASP、JS代码实现CHECKBOX选中内容后与TEXTAREA内容合并。
TEXTAREA原有内容修改后，可以与CHECKBOX选中内容合并，选中内容可取消、可重选。
求帮忙看看怎么实现。多谢！
网上找到的代码如下，但不是我想要的效果：
<html>
<head>
<style type="text/css">
.style1 {
font-size: small;
}
</style>
<script type="text/javascript">
function test(form) {
var Q = document.getElementById("city");
Q.value =""
for (var i=0;i<form.elements.length;i++) {
var e = form.elements[i];
if (e.name == "sc" && e.checked == true) {
Q.value =Q.value + e.value + ","
}
}
}
</script>
<form name="form1" method="post" action="">
<table cellpadding="0" cellspacing="0">
<tr>
<td>
<input name="sc" value="Beijing" type="checkbox" class="style1" onclick="test(this.form)" ><span class="style1">
Beijing</span></td>
<td>
<input name="sc" type="checkbox" class="style1" id="sc" value="Shanghai" onclick="test(this.form)"><span class="style1">
Shanghai</span></td>
</tr>
<tr>
<td>
<input name="sc" value="Xian" type="checkbox" class="style1" onclick="test(this.form)" ><span class="style1">
Xi'an</span></td>
<td>
<input name="sc" value="Guilin" type="checkbox" class="style1" onclick="test(this.form)" ><span class="style1">
Guilin</span></td>
</tr>
<tr>
<td>
<input name="sc" value="Lhasa" type="checkbox" class="style1" onclick="test(this.form)" ><span class="style1">
Lhasa, Tibet</span></td>
<td>
<input name="sc" value="Yangtze" type="checkbox" class="style1" onclick="test(this.form)"><span class="style1">
Yangtze River</span></td>
</tr>
</table>
<textarea name="city" id="city" rows="2" class="style1">原有内容</textarea>
</form>
因为对JS语言了解甚少，希望能帮忙改好。万分感谢！万分感谢！
