Key Lime Cupcakes

box lemon cake mix

box (4-serving size) lime-flavored gelatin

water

Key lime juice

vegetable oil

eggs

or 3 drops green food coloring

powdered sugar

to 2½ tablespoons Key lime juice

pkg light cream cheese, softened

butter, softened

vanilla

powdered sugar

fresh limes, each cut into 6 slice and cut slice in half