For the cake, mix the cake mix, gelatin, oil, eggs and orange juice in mixing bowl. Beat at medium speed for 3 minutes. Pour into three greased and floured 8 or 9 inch cake pans. Bake at 350 for 25 minutes or til cakes test done. Cool in pans for 10 minutes. Remove to wire rack.
Mix the powdered sugar and Key lime juice in bowl and mix well. Spread over warm cake layers and let cool completely.
For the icing, beat cream cheese and butter in mixing bowl. Beat in vanilla and powdered sugar til smooth. Spread between layers and over the top and side of the cooled cake.