fckeditor on root for multiple aliasses

Hi,

So let me explain quickly my implementation:
I am in an Intranet and have got my webserver
On the root of this web server I have copied the fckeditor directory
As I have to manage portals for different companies I have different aliasses : Company1 , Company2 ...
for each company I wish to have a usefile so that uploads are not shared between the companies

I use php language

I tryed to do this:
in the config.php file :

// Path to user files relative to the document root.0
$Config['UserFilesPath'] =  $_SESSION['FCKUserFilesPathREL'] ;
// Fill the following value it you prefer to specify the absolute path for the
// user files directory. Useful if you are using a virtual directory, symbolic
// link or alias. Examples: 'C:\\MySite\\userfiles\\' or '/root/mysite/userfiles/'.
// Attention: The above 'UserFilesPath' must point to the same directory.
$Config['UserFilesAbsolutePath'] = '';

and then juste before calling the editor I did:

$_SESSION['FCKUserFilesPathREL']= ???? 'Company1/userfiles/' //here I do not know the base for relativeness';
require_once($_SERVER['DOCUMENT_ROOT']."/fckeditor/fckeditor.php") ;

and before settong the editor:

$_SESSION['FCKUserFilesPathREL']='../../../../../../COmpany1/userfiles/';
require_once($_SERVER['DOCUMENT_ROOT']."/fckeditor/fckeditor.php") ;

When I launch the editor and open the file dialog and click on explor server I end up in this directory instead:
root\fckeditor\editor\filemanager\connectors\php

How can I mange to set the session variable to point to the right userfile folder for each company ?

[edit]
Just though It would be better if I gave also the code for the editor in the paeg :

$oFCKeditor = new FCKeditor('TexteFlash') ;   
                      $oFCKeditor->BasePath ='/fckeditor/' ;  
            $oFCKeditor->ToolbarSet="Basic";
            $oFCKeditor->Value = $rsActu['TextFlash'];
            $oFCKeditor->Height= '500';
            $oFCKeditor->Create() ;

What is most raging is that I had it working yesturday morning, then I changed something and it doesn't work anymore