1) you would need to hand code this with jquery Autocomplete:
http://jqueryui.com/autocomplete/
2) the onclick event on the home page is set to load the products_detail_item.php page, but that is not the page you included
onclick="document.location.href='../products_detail_item.php?ProductID=<?php echo($row_WADAproducts['ProductID']); ?>
<?php echo(isset($_GET["pageNum_WADAproducts"])?"&pageNum_WADAproducts=".intval($_GET["pageNum_WADAproducts"]):""); ?>';"
please send a copy of the products_detail_item.php page.