In a mixing bowl, combine cake mix, gelatin, oil and milk; mix until blended Add eggs, one at a time, beating well after each addition. Fold in blackberries, coconut and pecans. Pour into three greased 9-inch round baking pans. Bake at 350 for 25 to 30 minutes or until cake tests done; cool in pan 10 minutes before removing to wire racks.
Icing: Cream butter in a mixing bowl. Add sugar and milk; beat until des consistency is reached. Stir in blackberries, coconut and pecans. Frost to of two layers; stack on serving plate with plain layer on top. Frost top a sides of cake.