Soak gelatin in milk, in custard cup. Set cup in boiling water; stir until gelatin is completely dissolved. Combine yogurt, sugar, and salt. Stir in gelatin mixture. Stir in berries and lemon juice. Chill until slightly thickened; beat until foamy. Fold in whipped cream. Pour mixture in metal ice-cube tray. Cover with foil; freeze. NOTE: I have also made this with approx 1/2 of 1 pint of fresh strawberries, well crushed. I then froze it in a Donvier ice cream maker. Delicious!