Multiple Category Search

I found the solution…

My functions page now looks like:

<?php
    class dropdown extends Walker_CategoryDropdown {
        function start_el(&$output, $category, $depth, $args) {
            $pad = str_repeat('&nbsp;', $depth * 3);
            $cat_name = apply_filters( 'list_cats', $category->name, $category );
            $output .= "\t<option class=\"level-$depth\" value=\"".$category->slug."\""; 
            $output .= '>';
            $output .= $pad.$cat_name;
            if ( $args['show_count'] )
                $output .= '&nbsp;&nbsp;('. $category->count .')';
            if ( $args['show_last_update'] ) {
                $format="Y-m-d";
            $output .= '&nbsp;&nbsp;' . gmdate($format, $category->last_update_timestamp);
            }
            $output .= "</option>\n";
        }
    }
?>

My form now looks like:

<form method="get" id="searchform" action="<?php echo home_url(); ?>">
    <input type="text" onclick="this.value="";" onfocus="this.select()" onblur="this.value=!this.value?'Product Search...':this.value;" value="Product Search..." name="s" id="s" class="left" />
    <input type="image" src="https://wordpress.stackexchange.com/questions/50438/<?php bloginfo("template_directory') ?>/images/icosearch.png" id="searchsubmit" value=""/>
    <?php
        wp_dropdown_categories(
            array(
                'child_of' => 426,
                'class' => 'styled',
                'id' => 'make',
                'name' => 'make',
                'show_option_all' => 'Make...',
                'taxonomy' => 'product_cat',
                'walker' => new dropdown
            ))
    ?>
    <?php
        wp_dropdown_categories(
            array(
                'child_of' => 427,
                'class' => 'styled',
                'id' => 'model',
                'name' => 'model',
                'show_option_all' => 'Model...',
                'taxonomy' => 'product_cat',
                'walker' => new dropdown
            ))
    ?>
</form>

My search page now looks like:

<?php
    $tmp[]=$_GET["model"];
    $tmp[]=$_GET["make"];
    $product_cat=array();                                          
    foreach($tmp as $v) {
        if($v!="0")
        $product_cat[]=$v;
    }
    if(count($product_cat)>0) {
        $product_cat="&product_cat=".implode(",",$product_cat);    
    }
    else {
        $product_cat="";
    }                                                           
    $query=query_posts("s=$text".$product_cat);
    $count =count($query);
    if ($count == 0) { 
        echo 'No Results'; 
    }
    elseif ($count == 1) { 
        echo ''.$count.' Result'; 
    } 
    else { 
        echo ''.$count.' Results'; 
    } 
?>