Combine the zucchini, yellow squash, carrots, onion and water in a skillet. Cover and cook over medium heat for 4 to 5 minutes, or until the vegetables are tender. Add the margarine. Saute, uncovered, until all the moisture has evaporated. Serve immediately. Serves 2 One Serving = Calories: 94 Carbohydrates: 14 Protein: 3 Fat: 4 Sodium: 83 Potassium: 453 Cholesterol: 0 Exchange Value: 2 Vegetable Exchanges + 1 Fat Exchange