In a small saucepan, dissolve Knox gelatin in 1/4 cup cold water. Turn heat on low. Add crushed pineapple, sugar, and lemon juice. Stir and bring to a boil. Remove from stovetop and let cool completely.
In a mixer, mix Dream Whip according to package directions. Add the cream cheese and Carnation milk to the Dream Whip and beat well. Remove from mixer and fold in the Knox/pineapple/sugar/lemon juice mixture using a spoon. Pour into a long dish and refrigerate overnight. Keep refrigerated.