Auction House Buy Now Macro/Script

Hi all, I’ve heard of AddOns that let you do the instant-buy thing. Allegedly this is possible in-game without the use of an AddOn. I was wondering how you do it.

I heard about script/macros such as:
/run AuctionHouseFrame.BuyDialog.BuyNowButton:Click()

But this doesn’t seem to work for me. Any other way to instantly buy something you see on the list? Thanks!