function network_menu_page_url()

function.network_menu_page_url.php

<?php
/**
 * Get the URL for a network plugin page.
 *
 * @param string $menu_slug
 * @param string $parent_file
 * @return string|bool Url or FALSE on failure
 */
function network_menu_page_url( $menu_slug = '', $parent_file = '' ) {

	if ( '' === $menu_slug ) {
		if ( empty ( $GLOBALS['plugin_page'] ) )
			return FALSE;

		$menu_slug = $GLOBALS['plugin_page'];
	}

	if ( '' === $parent_file ) {
		if ( empty ( $GLOBALS['parent_file'] ) )
			return FALSE;

		$parent_file = $GLOBALS['parent_file'];
	}

	$url = add_query_arg(
		'page',
		$menu_slug,
		network_admin_url( $parent_file )
	);

	return esc_url( $url );
}