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Thanks for your reply. I am already using query strings but my main problem is that its defaulting to the orignal query. If you go here first select “date” from the filterby drop down and then select “show per page” and choose an value, it defaults to the original query I need to store the results some how.

Here is my code:

<?php if($_GET['amount']) {
			  			$show_per_page = $_GET['amount'];

			 	 }else{
					$show_per_page =10;
				}
				?>
				  <?php  $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;

						 query_posts("post_type=authors&posts_per_page=$show_per_page&paged=$paged"); ?>

            <?php  if(function_exists('wp_pagenavi')) { wp_pagenavi(); }?>

         <?php echo my_search_form(); ?>

         <?php if (class_exists('WP_Smart_Sort'))
					{ $wpss = new WP_Smart_Sort();
						if (method_exists($wpss,'placesort')) {
							$wpss->placesort();
						}
				} ?>
          <form action="" method="get">
              <select id="select-amount" name="" onChange="document.location.href=this.options[this.selectedIndex].value;">
              <option value="">Show per page</option>
              <option value="?amount=5">5</option>
              <option value="?amount=10">10</option>
               <option value="?amount=30">30</option>
               <option value="?amount=40">40</option>
              </select>
             </form>