try to change the order status to hold after thank you message displays. for this use checkout_onepage_controller_success_action event to change the order status.
<events>
<checkout_onepage_controller_success_action>
<observers>
<change_order_status>
<class>YourPackageName_YourModuleName_Model_Observer</class>
<method>changeOrderStatus</method>
</change_order_status>
</observers>
</checkout_onepage_controller_success_action>
</events>
and function is as follows
class YourPackageName_YourModuleName_Model_Observer{
public function changeOrderStatus($observer){
$orderIds = $observer->getEvent()->getOrderIds();
foreach ($orderIds as $orderId) {
$order = Mage::getModel('sales/order')->load($orderId);
$quoteId = $order->getQuoteId();
// this is how we get quote id from order.
// now add your logic here for shortlisting orders to be made on hold
}
}
}