Spicy "Jerk" Chicken

Found this online....spicy and yummy!  Great to change up the BBQ meals, and good shredded on a sandwich.

6 chicken breasts, sliced in half butterfly-style
3/4 T black pepper
1 1/2 T cumin
1 T chili powder
1 1/2 T brown sugar
3/4 T white sugar
2 1/2 T paprika
1 1/2 T salt
2 T garlic powder
3/4 T celery salt

Mix all dry ingredients in a ziplock bag.  Add in chicken pieces, seal and shake.  Make sure each piece is evenly coated.  Refrigerate for up to 1 hour.  Grill chicken over medium heat until done.