Preheat Grill For High Heat. In A Medium Bowl, Mix The Ground Beef, Bread Crumbs, Egg, Green Onions, 1 Tablespoon Cajun Seasoning, And Mustard. Form Into 4 Patties. In A Small Bowl, Blend The Barbeque Sauce And 1 Teaspoon Cajun Seasoning. Lightly Oil The Grill Grate, And Cook The Patties 5 Minutes Per Side, Or Until Well Done. Place A Slice Of Cheese On Each Burger, And Allow To Melt. Serve With Seasoned Barbeque Sauce.