fckeditor on root for multiple aliasses

// 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'] = '';

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

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

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