Lightly oil an 11- to 12-cup mold; set aside.

Pour 2 cups boiling water over the strawberry-flavored gelatin; stir until the gelatin is dissolved. Carefully stir in the frozen strawberries. Chill until the mixture begins to thicken. To quick-chill gelatin, place the bowl of gelatin over a bowl of ice water; stir until partially set. Stir to evenly distribute the strawberries and turn the mixture into the prepared mold. Refrigerate.

In a small bowl beat cream cheese, sour cream, salad dressing or mayonnaise, and lemon juice until the mixture is smooth.

In a small custard cup sprinkle the unflavored gelatin into 1/4 cup cold water. Place the custard cup in a skillet with 1/2 inch of boiling water. Stir the gelatin until dissolved. Stir the unflavored gelatin mixture into the cream cheese mixture. Beat until well blended. Carefully spoon the gelatin-cream cheese mixture over the strawberry mixture. Spread the gelatin-cream cheese mixture evenly to the edge of the mold. Refrigerate.

Pour 2 cups of boiling water over the blackberry-flavored gelatin and stir until the gelatin is dissolved. Add 1/2 cup cold water and the blueberries; stir. Chill until the mixture begins to thicken. Stir again to distribute the blueberries. Spoon the mixture over the cream cheese layer in the mold and spread evenly to the edge of the mold.

Refrigerate the gelatin mold until it is firm, overnight or several hours. Unmold onto a serving dish.

To unmold gelatin, loosen the edges of the mixture from the sides of the mold with the tip of a sharp knife or thin metal spatula. Set the mold in warm (not hot) water to the depth of the gelatin contents. Hold about 5 seconds. Tilt or shake the mold gently to loosen. Invert the serving plate on top of the mold. Hold both together firmly and invert. Shake the mold gently until the gelatin slips from the mold onto the serving dish or plate. If the gelatin doesn't release, repeat the process. Makes 12 servings.

For a successful layered gelatin salad, add the second layer when the first layer appears firm but is slightly sticky to the touch. At this stage the gelatin will retain a fingerprint. If the first layer is chilled too long, the second layer won't adhere; if it is not chilled long enough, the layers run together.