Custom redirect Add to Cart Magento

Question

I have a custom page where the customer will be redirected when he/she orders more than the remaining inventory of the product.

Here's my scenario :

Product 1 remaining inventory is 5 and the customer input a quantity 10 and pressed the Add to Cart button.

If the scenario above happens, i want to redirect to my custom page called http://www.example.com/errorcartpage

Is this possible? If yes, how do i do this?

P.S. Even though magento has default redirect if the scenario above happens, i still want to redirect to a custom page. It's a requirement.

Thanks

Answer 1

Use event catalog_product_type_prepare_full_options

`class Company_Example_Model_Observer
{
    public function catalogProductTypePrepare($observer)
    {
        $quote = Mage::getSingleton('checkout/session')->getQuote();
        if( your-condition-here){
            // do the magic here
        }
    }
}`