Non mi funziona, ti posto il codice intero:

if marca="" then
%><form name="form1" method="post" action="sele.asp?o=<%=o%>&iscr=<%=iscr%>&t=<%=t%>& marca=<%=marca%>">
<%
else
%>
</p>


</p>
<form name="form1" method="post" action="sele2.asp?o=<%=o%>&iscr=<%=iscr%>&t=<%=t%> ">
<div align="center">


<font face="Trebuchet MS"></font>
<%
end if
if produttore="" then
set rsValues4=Conn.execute("select distinct(produttore) from scooter where tipo='"&t&"'")
%>
<font face="Trebuchet MS">Seleziona Marca</font>
<Select name="produttore" onchange="this.form.submit( );">
>
<option selected></option>
<%
do while not rsValues4.eof
%>
<option> <%=rsValues4(0)%> </option>
<%
rsValues4.movenext
loop
rsValues4.close
set rsValues4 = nothing
%>
</Select>
<input type="submit" name="Submit24" value="Aggiorna">
</p>


</p>



<%
else
%>
<font face="Trebuchet MS">Seleziona Marca</font>
<Select name="produttore" onchange="this.form.submit( );">
<option selected ><%=produttore%></option>
</Select>
<input type="submit" name="Submit242" value="Aggiorna">
</p>


</p>



<%
end if
if marca="" then
set rsValues=Conn.execute("select distinct(marca) from scooter where tipo='"&t&"'and produttore='"&produttore&"'")
%>
<font face="Trebuchet MS">Seleziona Scooter</font>
<Select name="marca" onchange="this.form.submit( );">
<option selected></option>
<%
do while not rsValues.eof %>
<option> <%=rsValues(0)%> </option>
<%
rsValues.movenext
loop
rsValues.close
set rsValues = nothing
%>
</Select>
<input type="submit" name="Submit2422" value="Aggiorna">
</p>


</p>



<%
else
%>
<font face="Trebuchet MS">Seleziona Scooter</font>
<Select name="marca" onchange="this.form.submit( );">
<option selected ><%=marca%></option>
</Select>
<input type="submit" name="Submit2423" value="Aggiorna">
</p>


</p>



<%
end if
%>
<%
set rsValues2=Conn.execute("select distinct(modello) from scooter where marca='"&marca&"' and tipo='"&t&"'and produttore='"&produttore&"'")
%>
<font face="Trebuchet MS">Seleziona Modello</font>
<Select name="modello" onchange="this.form.submit( );">
<option selected></option>
<%
do while not rsValues2.eof %>
<option> <%=rsValues2(0)%> </option>
<%
rsValues2.movenext
loop
rsValues2.close
set rsValues2 = nothing
%>
</Select>
<input type="submit" name="Submit" value="Invia">
</p>
</div>
</form>