Creating a variable to show if patient has a particular discipline

I am trying to create a report to shows all active patients, but mark those with a certain discipline assigned (Heal at Home) . They have multiple disciplines, so if they have it first and something else next, then my fields shows false. If they have it last, then it shows true. I believe I have to use a variable, but I can't remember how to set it up and to clear it out when the next patient comes up.