Make your posts in your PostGrid link to any URL in a custom field you choose

MP Stacks PostGrid with Link in custom field

function my_custom_field_links_for_postgrid( $permalink, $grid_post_id, $brick_id ){
		
	global $wp_query;
	
	//If this page is the page with the postgrid on it
	if ( $brick_id == '31981' ){
		
		$site_link = get_post_meta( $grid_post_id, 'your_custom_field_slug', true );
		
		//If there is a site link
		if ( !empty( $site_link ) ){
			return $site_link;
		}
		//If there is not a site link in the body
		else{
			
			//Use the normal permalink
			return $permalink;
		
		}
		
	}
	//Otherwise, if it is not the page with the postgrid on it
	else{
		
		//Use the normal permalink
		return $permalink;
		
	} 
	
}
add_filter( 'mp_stacks_postgrid_grid_post_permalink', 'my_custom_field_links_for_postgrid', 10, 3 );