How To Add Buy Now Button Side By Side With Add To Cart Button

[xaphene]

How will I create a buy now button ($button_buy_now) just like add to cart button ($button_add_to_cart) in the same place side by side.
It should add the product to the cart and open the cart in a modal asking the user to checkout or continue browsing.

[eCommerce Core]

Do you need javascript help or AbanteCart help?