Dynamically adding WYSIWYG to metaboxes

I am not sure if this is what you want: (Source: https://stackoverflow.com/questions/3493313/how-to-add-wysiwyg-editor-in-wordpress-meta-box)

add_action( 'add_meta_boxes', 'adding_new_metaabox' );              
function adding_new_metaabox() {   
    add_meta_box('html_myid_61_section', 'TITLEE Helloo', 'my_output_function');
}

function my_output_function( $post ) {
//so, dont ned to use esc_attr in front of get_post_meta
$valueeee2=  get_post_meta($_GET['post'], 'SMTH_METANAME_VALUE' , true ) ;
wp_editor( htmlspecialchars_decode($valueeee2), 'mettaabox_ID_stylee', $settings = array('textarea_name'=>'MyInputNAME') );
}


function save_my_postdata( $post_id ) {                   
if (!empty($_POST['MyInputNAME']))
    {
    $datta=htmlspecialchars($_POST['MyInputNAME']);
    update_post_meta($post_id, 'SMTH_METANAME_VALUE', $datta );
    }
}
add_action( 'save_post', 'save_my_postdata' ); code here