Place cream cheese in large mixing bowl to soften, set aside.
In bowl of processor or chopper, add celery and carrot. Pulse until finely chopped.
Pour mixture onto the cream cheese. Add onion.
Stir until well-blended.
Keep refrigerated until ready to use.
If you have a larger sized food processor, you may add cream cheese, celery and carrots at the same time and pulse. Then gently add the onion.