Our site needs to be be able to add an item to the cart based on the users shipping location during the checkout process, for instance if they are shipping to Canada, a surcharge with a SKU will need to be added, it's a requirement of the ERP for the surcharge to be represented as an item with a SKU.
Is it possible to add an item to the cart while the user is on the one page checkout after the user chooses the shipping method? And based on location chosen add the surcharge product without redirecting the user back to the cart page?
I've done some research and so far I found that I can tie into an Observer event using the following
but from what I can tell, if the cart is updated while on the one page checkout, the user is auto redirected back to the cart page. I'm a little stumped so any help would be appreciated.