set custom discount amount in create order magento in quote and order

Question

I want to give custom discount to user while creating order from the backend and i have used code from http://pradeepkumarrcs.blogspot.in/2011/12/applying-custom-discount-amount-in.html and it is working fine in applying discount in the Quote but it is not updating the discount in the order. It shows discount amount in the cart but when I create order then there it shows zero Discount. Is there anything extra that i need to do? Function which i have used is:-

public function setDiscount($quote,$quoteid)
{
   $discountAmount=10;
if($quoteid) {
    if($discountAmount>0) {
        $total=$quote->getBaseSubtotal();
        $quote->setSubtotal(0);
        $quote->setBaseSubtotal(0);

        $quote->setSubtotalWithDiscount(0);
        $quote->setBaseSubtotalWithDiscount(0);

        $quote->setGrandTotal(0);
        $quote->setBaseGrandTotal(0);


        $canAddItems = $quote->isVirtual()? ('billing') : ('shipping');    
        foreach ($quote->getAllAddresses() as $address) {

        $address->setSubtotal(0);
        $address->setBaseSubtotal(0);

        $address->setGrandTotal(0);
        $address->setBaseGrandTotal(0);

        $address->collectTotals();

        $quote->setSubtotal((float) $quote->getSubtotal() + $address->getSubtotal());
        $quote->setBaseSubtotal((float) $quote->getBaseSubtotal() + $address->getBaseSubtotal());

        $quote->setSubtotalWithDiscount(
            (float) $quote->getSubtotalWithDiscount() + $address->getSubtotalWithDiscount()
        );
        $quote->setBaseSubtotalWithDiscount(
            (float) $quote->getBaseSubtotalWithDiscount() + $address->getBaseSubtotalWithDiscount()
        );

        $quote->setGrandTotal((float) $quote->getGrandTotal() + $address->getGrandTotal());
        $quote->setBaseGrandTotal((float) $quote->getBaseGrandTotal() + $address->getBaseGrandTotal());

        $quote ->save(); 

           $quote->setGrandTotal($quote->getBaseSubtotal()-$discountAmount)
           ->setBaseGrandTotal($quote->getBaseSubtotal()-$discountAmount)
           ->setSubtotalWithDiscount($quote->getBaseSubtotal()-$discountAmount)
           ->setBaseSubtotalWithDiscount($quote->getBaseSubtotal()-$discountAmount)
           ->save(); 


            if($address->getAddressType()==$canAddItems) {
            //echo $address->setDiscountAmount; exit;
                $address->setSubtotalWithDiscount((float) $address->getSubtotalWithDiscount()-$discountAmount);
                $address->setGrandTotal((float) $address->getGrandTotal()-$discountAmount);
                $address->setBaseSubtotalWithDiscount((float) $address->getBaseSubtotalWithDiscount()-$discountAmount);
                $address->setBaseGrandTotal((float) $address->getBaseGrandTotal()-$discountAmount);
                if($address->getDiscountDescription()){
                $address->setDiscountAmount(-($address->getDiscountAmount()-$discountAmount));
                $address->setDiscountDescription($address->getDiscountDescription().', Custom Discount');
                $address->setBaseDiscountAmount(-($address->getBaseDiscountAmount()-$discountAmount));
                }else {
                $address->setDiscountAmount(-($discountAmount));
                $address->setDiscountDescription('Custom Discount');
                $address->setBaseDiscountAmount(-($discountAmount));
                }
                $address->save();
            }//end: if
        } //end: foreach
        //echo $quote->getGrandTotal();

    foreach($quote->getAllItems() as $item){
             //We apply discount amount based on the ratio between the GrandTotal and the RowTotal
             $rat=$item->getPriceInclTax()/$total;
             $ratdisc=$discountAmount*$rat;
             $item->setDiscountAmount(($item->getDiscountAmount()+$ratdisc) * $item->getQty());
             $item->setBaseDiscountAmount(($item->getBaseDiscountAmount()+$ratdisc) * $item->getQty())->save();

           }


        }

    }
 }

Thanks In Advance.