Well, people should quit smoking. That just makes sense. But if you want to keep smoking, just smoke when you need one. Stop the truck and step outside. You have tons of precedent if they get on you about stopping to smoke. First of all, office people take little breaks to go smoke. And you can say you have an addiction to a legal substance that affects your behaviour. You can't be expected to be at your best when you are craving the drug that controls your life. Tell them it's a medical/physiological problem that you don't have control over. If they continue, consult a lawyer.