Twenty Eleven Excerpt Length

Just wondering if there would be anyway to pass a number, on a per template basis, to:

function twentyeleven_excerpt_length( $length ) {
	return 40;
}
add_filter( 'excerpt_length', 'twentyeleven_excerpt_length' );

Instead of it returning 40 for all excerpts it could return the passed variable that way having custom excerpts lengths in different templates etc…