In plastic bag, mix together garlic powder, chili powder, paprika and flour; add chicken and turn to coat. In large nonstick frypan, place olive oil over medium-high heat. Add chicken and cook, turning, about 7 minutes or until fork can be inserted with ease. Drizzle hot sauce over chicken, toss to coat; set aside. In medium bowl, mix together onion, cucumber and ranch dressing. Inside each bun, place 1 lettuce leaf and top with chicken and celery; spoon onion-cucumber mixture on top. Sprinkle with blue cheese.