Chicks in danger

[igorsMistress]

I think your best bet is lock your door and/or put up a sign for Grandma. Unless you have a large dog crate or a way to put a lid on your box, those are really your best options. Also, do you have your coop ready? 10 chicks will outgrow your brooder pretty quickly.
Your profile doesn't say where you're located, but if you can your chicks outside in a coop to nrood you could also solve the problem

 

[chickens really]

I would rethink the cardboard box your using. In a week or so they will be jumping out..A plastic tote with a wire top would work.
Best wishes with the Chicks..