The mousse mixture will set quickly after gelatin is added; be sure to assemble in the following order. Whip cream until soft peaks form. Set aside. Soften gelatin in cold water, heat in top of double boiler until dissolved; cool, mixture should still be liquid. Beat cream cheese and sugar until light and fluffy. Add vanilla, milk and lemon juice, mix. Add dissolved gelatin, stir. Immediately fold in whipped cream. Pour into prepared pan. Refrigerate until firm.