In 3-quart saucepan, cook macaroni as directed on package, adding frozen broccoli during last 3 to 5 minutes of cooking time; drain and return to saucepan.
Meanwhile, in 2-quart saucepan, heat cooking sauce and pumpkin to boiling over medium heat, stirring constantly with whisk. Reduce heat. Add cheese and nutmeg; stir until cheese is melted.
Add cheese sauce to macaroni and broccoli; toss to coat.