Coat a nonstick skillet with cooking spray; place over medium-high heat until hot. Add carrot, onion, and beans. Saute until tender.
Combine broth, water, and salt in a small saucepan; bring to a boil. Remove from heat. Add couscous; cover and let stand 5 minutes or until couscous is tender and liquid is absorbed. Fluff couscous with a fork. Add vegetable mixture and Italian dressing; toss lightly.