Inpatient rehab programs require you to focus on healing. In many cases, it is not possible to continue working during the course of your treatment.
With that said, there are exceptions. People who work remotely or executives who can operate crucial aspects of business over the phone may be able to do some work during off-hours.
To find out more information, contact your treatment provider. Many rehab centers have rules around the use of electronics that could also affect your ability to work.