<?php

class Orange35_CustomInvoicesGenerator_Model_Resource_Invoice_Collection extends Mage_Core_Model_Resource_Db_Collection_Abstract
{
    protected function _construct()
    {
        $this->_init('orange35_custominvoicesgenerator/invoice');
    }

    public function getInvoicesByOrderId($orderId)
    {
        $this->getSelect()->where("order_id = ". $orderId . " AND payment_status = '".ucfirst(Mage_Paypal_Model_Info::PAYMENTSTATUS_COMPLETED)."'");
        return $this;
    }
}