In a large microwave-safe bowl, combine the potatoes, carrots, celery and water. Cover and microwave on high for 5 ½ minutes, stirring once. Add green pepper and onion; cover and microwave on high for 3-4 minutes or until crisp-tender, stirring once. Pour into a 2-qt. Microwave-safe baking dish coated with cooking spray; set aside.
In a microwave-safe bowl, heat the margarine, covered, on high for 30-40 secounds or until melted. Stir in the flour, salt and pepper until smooth. Gradually add milk.
Cook, uncovered, on high for 1 ½ to 2 minutes or until thickened and bubbly, stirring after each minute. Stir in the cheese until melted. Pour over vegetables. Stir in ham. Cover and microwave on high for 3-4 minutes or until heated through. Yield: 4 servings.