Mix the first two ingredients together and press firmly into an 8 x 8 baking pan. Bake for 12 minutes at 350°F. Remove from oven and set aside. Place the jelly and custard powder in a saucepan. Pour in 2 cups of boiling water and place on stove; while stirring constantly, bring this mixture to a boil. Remove from heat and pour over bottom mixture. Place in refrigerator to set firmly. In a small bowl place, the tin cream and the Dream Whip powder and beat well with an electric mixer. Place on top of the well-set jelly mixture. Let chill before cutting.