Problems "Top-level" plugin

[yxcvbnm]

i want to write a small "top-level" plugin (means: i use an additional tab next to the plugins tab in the menu')
in the main section of the plugin, i want to use a php file which renders my form.
i decided to put that into the admin/plugins/myplugin folder and added the tab with:

Code:

add_action('nav-tab', 'createNavTab', array(''plugins/myplugin/myplugin.php', 'My Plugin'));

the starting code of plugins/myplugin/myplugin.php, but the include of ../../inc/common.php fails. It fails, because include of cookie_functions:121 fails and that cause cookie_functions:9 inc_configuration.php fails). what can i do?

Code:

<?php

/****************************************************
*
* @File:     plugins.php
* @Package:    GetSimple
* @Action:    Displays all installed plugins.    
*
*****************************************************/
// Setup inclusions
$load['plugin'] = true;

// Relative
$relative = '../../../';
// Include common.php
include('../../inc/common.php');

// Variable settings
login_cookie_check();
$path = tsl('plugins');
$counter = '0';
$table = '';

?>