WP e-Commerce Many Vendors plugin help needed

Hello everyone,

I am using WP e-Commerce and Many Vendors 1.0 -Beta plugins.

I want to show the vendor specific products on Product Page by using only WP_Query().

$params=array(
	   'post_type' => 'wpsc-product',
	   'post_status' => 'publish',
	   'meta_query' =>
 		       array(
			   'wp_capabilities' => 'vendor',
			    '_wpsc_vendors'=> 'xyz'
			   )
		);

	    $vendar_query = new WP_Query($params);

I figure out the products are being saved in wp_posts table. Now question is, how can we read their relation with user(vendor) in meta_value of wp_postmeta table?

Thanks, in advanced.