I need some advice on how to create an exit strategy. So my neighbor came to me saying I have to walk his dog twice a day for the 3 weeks in July because he's going to go visit his family in India. Here's the problem I have:

1: my neighbor didn't bother asking if Im available to walk his. He just came out and said "I need you to walk my dog".

2: I work for one of our local public schools and in July, there's summer vacation. I can't go on vacation, I can't go sleep over my extended families house for 2 or 3 days, etc in July because I'll have to rearrange a good chunk of my summer vacation for a dog that I don't own and didnt agree to take care of

My question is, how do I approach him respectfully to let him know I'm not interested in taking care of his dog for 3 weeks?