updating href when onclick or onchange in drop down box/menu selection

hi!
I would like to know if there is a way to update a href link (without page reload) when a selection is made in a drop down box/menu?

for example:
[php]<?php
echo "<select name='subcat' onchange('function to append noticia[x] to href')><option value=''>Select caterogry</option>";
while (query=true){
echo "<option selected value='$noticia[x]>$noticia[y]</option>"."<BR>";}

?> [php]
<a href= localhost/?subcat=noticia[x] /a>

note: the page is not to be reloaded nor are the drop down boxes to be reset when selection is made in menu

thanks in advance

you proble want to use client size Javascript rather than server side code for this. Server side would require reloading to the best of my knowledge.