Squeeze the lime and orange juice into a bowl or measuring cup. Heat the cranberry juice and sugar in a saucepan over medium heat until the sugar has dissolved.I added some fresh cranberries cut in half, oranges and limes to my mix just to infuse a little more flavor.
Let the mixture cool a bit before adding in the lime juice, mix together, and pour into a bottle. Refrigerate the mix for up to two weeks.
To mix a margarita, just add a shot of silver tequila to a short glass filled with ice. Then top it off with the margarita mix.