Upgrade on the Cart and Checkout page to offer to order

Hi Team I'm using another app to offer Volume discount on one of my products.

But I'm seeing that some customers contact me two days later to do un upgrade on quantity ( the offer is more buy more save) so I want to add a Upgrade on the Cart and Checkout page to offer to order more of the same product so they can do it in that exactly moment. Can I do it with your app?