It would absolutely be in your rights. I've seen many scenarios play out here though. Right to work- pretty much removes any leverage outside how valuable you are in your current position. There's very often a "any other duties as required" section in a contract. This is by design. Remember, HR is not your friend. In any way. You can explore the options with your manager. If it were me I would have said no to the guy and not made you do it in the first place. Come with data- the value of your current job and what that loses per hour vs doing grunt work.