Olanzapine is occasionally prescribed off-label as an anti-anxiety, and drowsiness is a commonly reported side effect, so you can certainly get some of the desired traits that benzos typically offer.
As an antipsychotic, a typical starting dose of olanzapine is on average between 10-15mg and an average maintenance dose is 20-50mg, so I think you'll be okay with the 40mg that you have, although I certainly doubt it will have the same effectiveness as a benzodiazepine class drug.
Olanzapine has many interactions, if you are on other medications, I suggest you search online to safeguard against unwanted reactions.