[dahamsta]

For the record, you need to include global.php, then the Paid Subscriptions class. Example:

chdir('/path/to/vbulletin');
require_once('global.php');
require('includes/class_paid_subscription.php');
$sub = new vB_PaidSubscription($vbulletin);
$sub->build_user_subscription(1, 0, $userid);

Where 1 is the subscriptionid, which you can get by going to the Subscription Manager and mousing over Active or Total; and 0 is the cost identifier, starting from 0 and working down.

HTH,
adam