In a small bowl combine chicken, sherry, salt and cornstarch. Let stand 15 minutes.
Heat 1 tablespoon oil in a skillet or wok. Add chicken and stir fry until cooked through – about 3-4 minutes. Remove cooked chicken to a medium bowl.
Heat an additional 3 tablespoons oil in the pan, then add celery. Stir fry 2-3 minutes. Add sugar and water. Cover and steam for one minute. Remove cover and stir fry until liquid evaporates. Add cooked celery to bowl with chicken.
Add bean sprouts and lettuce to bowl and mix. Set aside to cool.
Roll wrappers into egg rolls using 1-2 tablespoons of filling for each.
Deep fry egg rolls for about 2-4 minutes, until crispy and brown.