请问怎么验证一个IP地址只能投一次票啊?
<form action="tj/tao.asp"method="post"name="myform"onsubmit="javascript:return check()"><table align="right"bgcolor="#660099"width="350"height="142">
<tr><td align="right">
<input type="hidden"name="ip"value="<%=request.servervariables("remote_addr")%>">
<input type="radio" name="n1" value="d1">
</td><td>
<font color="#FF0099">美观度好</font>
</td></tr>
<tr><td align="right">
<input type="radio" name="n1" value="d2">
</td><td>
<font color="#FF0099">信息含量高</font>
</td></tr>
<tr><td align="right">
<input type="radio" name="n1" value="d3">
</td><td>
<font color="#FF0099">交流平台好</font>
</td></tr>
<tr><td align="right">
<input type="radio" name="n1" value="d4">
</td><td>
<font color="#FF0099">服务覆盖面广</font>
</td></tr>
<tr><td align="right">
<input type="submit"value="投票"onclick="vbscript:location.href='tj/yanzheng.asp'">
</td>
<td align="left">
<input type="button"value="查看" onclick="vbscript:location.href='tj/ca.asp'">
</td></tr>
</table>
</form>
请问该怎样修改这段代码才能实现一个IP地址只能投一次票,或者修改(tj/tao.asp)文件,小弟弄好几天还是不行啊!请各位师哥师姐指教,小弟在此说声谢谢!