Filtering by sub category [Advanced] using Ajax

Hi guys,

I was using this: Code here (Stackoverflow)

I managed to customize the code to where I want it. It works 100% and the code is as shown below:

<?php

		function my_subcat_filter($post_type_id = 'company_listing', &$filter_get_value, $echo = TRUE) {

		    $this_category = get_category(get_query_var('cat'),false);
		    $mycat_ID = (int)get_query_var('cat');
		    $myresults = get_categories('&child_of='.$mycat_ID.'&hide_empty');

		    $myfield = array();
			    foreach ($myresults as $myres) {
			    	$myfield[] = $myres;
			    }

			// query current category id
			$this_category = get_category(get_query_var('cat'),false);
			$cat_ID = (int)get_query_var('cat');
			//$filter_get_value = isset($_GET[$filter_id] : )
			$myfilter = wp_dropdown_categories( array (
					'show_option_all' => 'All',
					'child_of' => $cat_ID,
					'hide_empty' => 0
					)
				);
my_subcat_filter('product', $product_filter);
		$args = array('post_type' => 'company_listing', 'orderby' => $product_filter);
		// The end
	?>

What I want to do now is to have the user category selection to filter using the Ajax or alternative. Loads the custom post based on what category is / was selected from the drop down menu.

Let me know if you need anything extra.