Four gelatin layers, each a mixture of: 3 ounce package of flavored gelatin, 1 envelope Knox gelatin, 1 cup boiling water. Three milk layers made by dividing into thirds a mixture of: 1 can sweetened condensed milk, 2 cups boiling water, 4 envelopes Knox gelatin. Use 9 x 13 inch pan, leveled on a refrigerator shelf. Prepare milk mixture; divide into thirds. Keep them warm, (liquid) until use. Prepare one Jello layer. Pour into level 9 x 13 inch pan. Allow to gel until just set, about 20 minutes. Second layer, 1/3 of milk mixture. Spoon on each layer gently over previous layer. Alternate gelatin layer and milk layers. Chill overnight before cutting into squares to serve.