Upselling products..

Hey --

Just a quick question. I want to upsell products on my shop. But somewhere in the checkout process. Ideally, I want them to add credit card details, and hit 'submit order'. Then at this moment, it pauses the order for a second and gives them the option to add other products to their cart at a discount.. then, adding those products or not, and then charging the card. Is it possible?