Lightly grind up a package of cranberries in a food processor. Place berries in a large heavy skillet and stir and cook for 10 minutes unti berries begin to soften and release their moisture. Add 3/4 cup of sugar and stir til boiling. Continue boiling for an additional 10 minutes til the cranberries begin to mush together. Stir in the jar of orange marmalade and continue cooking til marmalade melts and sauce is thickened.
Do not leave the stove while cooking this---sugar can burn easily if you are not continually stirring.