In a small bowl stir together salad dressing and mustard. Stir in coleslaw mix; mix well.
Spread a thin layer of margarine or butter on one side of each piece of bread; turn bread over. Top four of the bread slices with half of the ham. Spoon coleslaw mixture on evenly, and top with sliced cheese and remaining ham. Finish by topping with remaining bread slices, margarine side up.
Heat a large skillet or griddle. Cook sandwiches over medium-low heat for 2 to 3 minutes or until golden; turn sandwiches over. Cook 2 to 3 minutes more or until golden and cheese starts to melt. Makes 4 servings.