Dog food dilemma

Sticky has no teeth so we have to give her special food, Pippin loves this food but he isn't allowed to have it because he has allergies.

We tried to put the food in a room with a small dog door, but no one could keep it closed, so I decided to make something out of a cardboard box. The hole in which Sticky would get in was too big, so I made it smaller and smaller and smaller and he still could get in, so I changed the design at this point, I had made two very small holes, and he still got in.

I'm still working on the design but I adjusted this one and it looks good.