Dear Boss,

I don't work Wednesday afternoons. I'm never here on Wednesday. Please stop trying to schedule meetings on Wednesday afternoon. I won't be here. If there's something that needs to be done by Wednesday afternoon, you need to get your part done in time for me to get it done before I leave on Wednesday. I'm not staying two hours late to get it done because you forgot (again) that I don't work on Wednesday afternoons (every Wednesday). Please try to remember next week. I won't be here Wednesday afternoon.