<script language="javascript">
function dd(tvalue)
{
window.navigate("self.asp?s2value="+tvalue)
}
</script>
<select size=1 name="select1" onchange="dd(this.value)"
.....
<select size=1 name="select2">
<%
if request("s2value")="" then
(default code)
else
(make your sql string)
end if
....
do until rs.eof
response.write("<option.....")
loop
%>