Using Apple Store Gift Card from Trade-in

Is there a way to apply an Apple Store gift card on a previous purchase?

I am looking to buy a refurbished MacBook Pro 15.4-in from Apple; however, I understand that Apple does not let you set up a trade-in in the checkout screen when purchasing a refurbished laptop. Thus, I was thinking of just using the mail-in trade in process to get an Apple store gift card to apply to my purchase for a refurbished laptop.

I use my current MacBook Pro for personal and work use, so I do not want to be out of a laptop for 2-3 weeks while I wait for it to get evaluated and I receive the gift card. I would much rather purchase the refurbished laptop that I like online, transfer my files over to the new laptop, and then mail in my current one laptop for credit. Thus, I was wondering if it’s at all possible to apply the Apple store gift card to the refurbished laptop AFTER I have already paid for it in full (such that I would be “refunded” an amount equivalent to that which is on the Apple store gift card). Is this something that is possible? Or alternatively, once I have both the refurbished laptop and the Apple store gift card, am I allowed to “return” the refurbished laptop in store, and then re-purchase it that same day but apply the gift card?

I’ve spoken with so many Apple representatives at this point and they all give me different answers. I just want to know so I can decide whether I should buy the refurbished laptop now or not.

Thank you!