Bring a pot of water to a simmer, and immerse green beans. Allow to cook for 5 minutes, or until almost done. Do not overcook. Drain.
Melt margarine over medium low heat in a large skillet, and add green beans. Allow to cook for a minute or two, then add cranberries and mango juice, gently tossing to combine well. Season with salt, and simmer for 3-4 more minutes, stirring occasionally, until most of the liquid has been absorbed.
Enjoy this unusual green bean side dish with at your Thanksgiving!