SELECT ドロップダウンメニューで VALUE と TEXT 値を同時に取得する ASP コード

<form action="reguser2.asp" method="post" name="form1" onSubmit="return checksumit();">
<table width="100%" border="1" cellspacing="0" cellpadding="0">
<tr>
<td> Town where.
<%
sql="select * from zhen"
set rs=server.createobject("adodb.recordset")
rs.open sql,conn,3,2
%>
<select name="zhen" id="zhen">
<option value=-1>select town</option>
<%
if rs.eof and rs.bof then
response.Write("<option value=-1>No town</option>")
else
do while not rs.eof
%>
<option value="<%=rs("z_id")%>"><%=rs("z_name")%></option> //here the values of value and text in database, but the variable "zhen" can only get the value of value... How do I get the selected text value?
<%
rs.movenext
loop
end if%>
</select></td>
</tr>
<tr align="center">
<td><input type="submit" name="Submit" value="Next" onclick="Javascript:callvalue()"& gt;</td> //Third step, pass to the next page button here to add onclick to get the value
</tr>
</table>

<input type="hidden" name ="sendvalue" /> //Step 1, add a hidden input control here
<script language="JavaScript"> //Second step, here write a function to get the text value
function callvalue() {
sendvalue = document.form1.zhen.item(document.form1.zhen.selectedIndex).text;
//alert(sendvalue);
document.form1.sendvalue.value = sendvalue;
form1.submit();
}
</script>