How do you handle a coworker who interrupts you when you say “I’m busy right now. I’ll be happy to help you later.” ?

I say “I’m busy right now. I’ll be happy to help you later.” (in a nice, polite, friendly tone)<br>Then, they stand there at my desk and continue talking and asking me questions about what I’m doing. Not saying “okay, I’ll ask later.” and walking away. Just standing there, asking questions, and expecting me to give them answers in the moment, while I’m busy. I will respond to the questions without even looking at them, but it seems like they are just trying to get a reaction out of me, and see if I will snap. I never do. I always handle things professionally and politely. But it is really frustrating.