Exempt employees: When can you dock their pay?

Q. "We require exempt employees who miss a full day for any reason to use either a sick day, personal day or vacation day in order to get paid for the full week. Is this appropriate? Is it permissible to pay them for less than a full week of work if they have used all of their paid leave time and still miss a full day of work? Which is it? Pay for the full week or dock one of the days?" -- Randy, Texas