Execute script only on certain admin pages

You can use this in your functions.php :

function add_admin_scripts( $hook ) {

    if ( $hook == 'post-new.php' ) {

        wp_enqueue_script(  'myscript', get_bloginfo('template_directory').'/js/myscript.js' );

    }
}
add_action('admin_enqueue_scripts','add_admin_scripts',10,1);