Melt margerine in a large saucepan over medium heat. Add onion and celery. Cook 5 minutes or until tender, stirring. Add broth and bring to a boil. Add potatoes and cook over low heat, about 25 minutes, until potatoes are soft, stirring occasionally. Add chiles and corn, and return to boiling. In a small bowl, dissolve the gravy mix in the milk. Stir it into the potato and broth mixture. Add cheese. Stir, and cook over low heat until cheese is melted. Serves 6 to 8.