In A Large Saucepan, Cook The Beef, Onion, Green Pepper And Celery Over Medium Heat Until Meat Is No Longer Pink And Vegetables Are Tender; Drain. Add The Tomatoes And Cajun Seasoning; Mix Well. Cook, Uncovered, For 15-20 Minutes, Stirring Occasionally. Meanwhile, Prepare Macaroni And Cheese, Suing 2 Tablespoons Milk And 1 Tablespoon Butter. Stir In Beef Mixture; Cook For 2-3 Minutes Or Until Heated Through.