I want to make something to block my little dog from going into a room

You can buy gates similar to toddler gates to close off a hallway or doorway. They make them with small animal passes in them like a cat or small dog can use but it is too small for a toddler or medium dog. It depends on the size of your dog if that would work. I hope this helps.

This is hard. I had so much trouble with this. My dog jumped over everything I tried. I would go to a pet store and speak with a expert about this. they might actually have something. Kid gates do not do the trick!

Baby gates work well depending upon the size of your pets. We used a single baby gate raised up so that the cats could crawl under. The dogs were too large to crawl under and I think a bit to stunned to realize that they could jump over LOL. You can use two baby gates, one on top of the other to make it high enough so the dog(s) can't jump over. Sadly we no longer have the dogs and I use two baby gates in my living room patio doorway, to keep the cat inside at night while letting the cooler air into the house (patio is screened but I don't want him out there alone at night-just in case). The cat doesn't bother trying to crawl up and over maybe he is a bit stunned like the dogs were LOL.

I purchased a dog gate with a small for my cat. Depending on how big/small you dog is, this would fix you situation. It goes between doors and is adjustable. It also opens for humans, It's perfect to keep my dogs out of the cat's litter box. I believe I got it through Amazon.

I have seen gates with a small opening for a cat, too. It will work for you IF your dog is too big for the opening.

There are pet doors that only open if the pet is wearing a particular tag that might work for you: https://www.chewy.com/cat-mate-electromagnetic-cat-flap/dp/103177?utm_source=google-product&utm_medium=cpc&utm_campaign=hg&utm_content=Cat%20Mate&utm_term=&gclid=Cj0KCQiA5aTUBRC2ARIsAPoPJk-mjLmGTnGoTqoLSHl6RdXPJ-DsdT00Y1NZs_ryfDe6SffABOaVTkwaAtW_EALw_wcB&gclsrc=aw.ds