Hello Arantxa,
I think the only option is to create a new publication record for the chapter and, after that, to set the dependency of the book in the relations group of the record. We use the same solution for papers and journals. This is the record of a journal in our system with the dependencies.
So, one record for the book and and another one for the record for the chapter is the best way for doing that.
I hope it helps.
Best