Get current Blog ID in Tinymce Plugin Dialog Window in WPMU

is there any way, to get the current blog id in a Tinymce Dialog Window? Currently I only get the id, from the main blog. This is my current code:

$wp_load = "wp-load.php";
while(!file_exists($wp_load)) {
$wp_load = '../' . $wp_load;
if(file_exists($wp_load)){
    break;
}
}
require_once($wp_load);
global $blog_id;
echo $blog_id;
$blog = get_blog_details($blog_id);

Any help is welcome.

Lars