Pass dynamic price from detailed page to cart in magento

I am a beginner in magento. I need to pass the dynamic price from detailed page to cart.

Right now when i pass the dynamic price it is not updating in the cart it is replaced by the original price of the product.

Any help will be appreciated. In this line I am getting the price value. $price=$this->getRequest()->getParam('price_custom'); Indexcontroller.php

public function cartAction()
    {
        if ($this->getRequest()->getParam('cart')){
            if ($this->getRequest()->getParam('cart') == "delete"){
                $id = $this->getRequest()->getParam('id');
                if ($id) {
                    try {
                        Mage::getSingleton('checkout/cart')->removeItem($id)
                          ->save();
                    } catch (Exception $e) {
                        Mage::getSingleton('checkout/session')->addError($this->__('Cannot remove item'));
                    }
                }
            }
        }

        if ($this->getRequest()->getParam('product')) {
            $cart   = Mage::getSingleton('checkout/cart');
            $params = $this->getRequest()->getParams();
            $related = $this->getRequest()->getParam('related_product');
            $price=$this->getRequest()->getParam('price_custom');
            $productId = (int) $this->getRequest()->getParam('product');


            if ($productId) {
                $product = Mage::getModel('catalog/product')
                    ->setStoreId(Mage::app()->getStore()->getId())
                    ->load($productId);
                try {

                    if (!isset($params['qty'])) {
                        $params['qty'] = 1;
                    }

                     $cart->addProduct($product, $params);




                    if (!empty($related)) {
                        $cart->addProductsByIds(explode(',', $related));
                    }

                    $cart->save();

                    Mage::getSingleton('checkout/session')->setCartWasUpdated(true);
                    Mage::getSingleton('checkout/session')->setCartInsertedItem($product->getId());

                    $img = '';
                    Mage::dispatchEvent('checkout_cart_add_product_complete', array('product'=>$product, 'request'=>$this->getRequest()));

                    $photo_arr = explode("x",Mage::getStoreConfig('mdlajaxcheckout/default/mdl_ajax_cart_image_size', Mage::app()->getStore()->getId()));

                    $img = '<img src="'.Mage::helper('catalog/image')->init($product, 'image')->resize($photo_arr[0],$photo_arr[1]).'" width="'.$photo_arr[0].'" height="'.$photo_arr[1].'" />';
                    $message = $this->__('%s was successfully added to your shopping cart.', $product->getName());
                    Mage::getSingleton('checkout/session')->addSuccess('<div class="mdlajax-checkout-img">'.$img.'</div><div class="mdlajax-checkout-txt">'.$message.'</div>');
                }
                catch (Mage_Core_Exception $e) {
                    if (Mage::getSingleton('checkout/session')->getUseNotice(true)) {
                        Mage::getSingleton('checkout/session')->addNotice($e->getMessage());
                    } else {
                        $messages = array_unique(explode("\n", $e->getMessage()));
                        foreach ($messages as $message) {
                            Mage::getSingleton('checkout/session')->addError($message);
                        }
                    }
                }
                catch (Exception $e) {
                    Mage::getSingleton('checkout/session')->addException($e, $this->__('Can not add item to shopping cart'));
                }

            }
        }
        $this->loadLayout();
        $this->_initLayoutMessages('checkout/session');

        $this->renderLayout();
    }

Observer.php

class Mdl_Ajaxcheckout_Model_Observer
{
    public function modifyPrice(Varien_Event_Observer $obs)
    {
        // Get the quote item
        $item = $obs->getQuoteItem();

        // Ensure we have the parent item, if it has one
        $item = ( $item->getParentItem() ? $item->getParentItem() : $item );

        // Load the custom price
        $price =$item->getRequest()->getParam('price_custom');
        // Set the custom price
        $item->setCustomPrice($price);
        $item->setOriginalCustomPrice($price);
        // Enable super mode on the product.
        $item->getProduct()->setIsSuperMode(true);
    }



}

Please Suggest.

Magento doesn’t offer the ability to add custom prices when adding items to your cart. This is a solution I’ve used on occasion.

You can use an observer class to listen to checkout_cart_product_add_after, and use a product’s “Super Mode” to set custom prices against the quote item.

In your /app/code/local/{namespace}/{yourmodule}/etc/config.xml:

<config>
    ...
    <frontend>
        ...
        <events>
            <checkout_cart_product_add_after>
                <observers>
                    <unique_event_name>
                        <class>{{modulename}}/observer</class>
                        <method>modifyPrice</method>
                    </unique_event_name>
                </observers>
            </checkout_cart_product_add_after>
        </events>
        ...
    </frontend>
    ...
</config>

And then create an Observer class at /app/code/local/{namespace}/{yourmodule}/Model/Observer.php

 class <namespace>_<modulename>_Model_Observer
{
    public function modifyPrice(Varien_Event_Observer $obs)
    {
        // Get the quote item
        $item = $obs->getQuoteItem();
        // Ensure we have the parent item, if it has one
        $item = ( $item->getParentItem() ? $item->getParentItem() : $item );
        // Load the custom price
        $price = "your custom price logic";
        // Set the custom price
        $item->setCustomPrice($price);
        $item->setOriginalCustomPrice($price);
        // Enable super mode on the product.
        $item->getProduct()->setIsSuperMode(true);
    }



}