An example of how to use wp_editor() on a custom WPAlchemy metabox.

wp_editor.php

<?
$mb->the_field( 'field_name' );
$content = apply_filters( 'meta_content', html_entity_decode( $mb->get_the_value() ) );
$id = $mb->get_the_name();
$settings = array(
	'textarea_rows' => 3
);

wp_editor( $content, $id, $settings );