edow on "Sidebar tag check sees only tags from first 9 posts"

Hi,

I use the following code in my category sidebar to check which tags are used in the category. It works, but only for the first 9 posts (the first page displays 9 posts.) How can I change this code so it also checks for the other posts in this category?

<?php

		if (is_category()){

		  $cat = get_query_var('cat');

		  $yourcat = get_category ($cat);

		}

		$tag_IDs = array();

		query_posts('category_name='.$yourcat->slug);

		if (have_posts()) : while (have_posts()) : the_post();

		  $posttags = get_the_tags();

		  if ($posttags):

			foreach($posttags as $tag) {

			if (!in_array($tag->term_id , $tag_IDs)):

			   $tag_IDs[] = $tag->term_id; 

			   $tag_names[$tag->term_id] = $tag->name;

			   $tag_slug[$tag->term_id] = $tag->slug;

			 endif;

			}

		  endif;

		endwhile; endif;

		wp_reset_query();

		$getTag = $_GET["tag"];

		if ($getTag == '') { 

			$tag_showall = 'checked';

			}

		if (!empty($tag_IDs)){

			echo '<h3>Aanbieders</h3>';

			echo '<input type="radio" name="tag" value="" '.$tag_showall.'> Alles weergeven<br>';

		}

		foreach($tag_IDs as $tag_ID){

			$checked = $tag_slug[$tag_ID];

			echo '<input type="radio" name="tag" value="'.$checked.'"' ;

			if((isset($_GET["tag"])) && $_GET["tag"] == $checked) {

			echo ' checked="checked"';

			}

			echo '> '.$tag_names[$tag_ID].'<br>';

		}

		?>