exclude categories on category combo

I need exclude categories 33, 34 & 35 from this combolist of categories. Someone can help me please? Im desperate!

<form action="<?php bloginfo('url'); ?>/" method="get">	<div><?php
$select = wp_dropdown_categories('show_option_none=Selecciona tu Provincia&show_count=0&orderby=name&echo=0');
$select = preg_replace("#<select([^>]*)>#", "<select$1 onchange='return this.form.submit()'>", $select);
echo $select;
?><noscript><div><input type="submit" value="View" /></div></noscript></div></form>