Pour tequila into a 12-ounce glass. Add Grand Marnier. Pour in lime juice, orange juice and sweet and sour mix. Cover the glass firmly with a cocktail shaker and shake to mix the ingredients.
Fill a margarita glass with ice, then pour the mixture into the glass, using a strainer to keep the ice out of the glass. Top with Chambord. Garnish with a skewer of two blackberries and one raspberry (or vice versa).