This is already a setting! Just make sure that your default core status button is set to what your shop realistically sees. In one of my locations, next door to Napa, cores get returned ASAP, so we leave it on core status retuned default. In my other location, this doesn't work, so you can either set it to unknown or not returned. If work orders staying open for over a month is a common issue, we also have a solution to that, so as not to mess up the reconciliation process.