Combine margarita mix, coriander, and garlic. Place pork cubes in heavy plastic bag; pour marinade over to cover. Marinate for at least 30 minutes. Blend together well the butter, lime juice, sugar, and parsley; set aside.
Thread pork cubes onto skewers, alternating with pieces of corn and pepper. (If using bamboo skewers, soak in water 20-30 minutes before using.) Grill over hot coals, basting with butter mixture, for 10-15 minutes, turning frequently.