Aaargh no! Cillit Bang is acidic, that is why it is so good at removing limescale. Your range cooker's enamel though has no real resistance to acid. Fruit acids, and even tomato juice will mark range cooker enamel with a dull white stripe. This is permanent I'm afraid and there is nothing that can be done except to replace the front or top of the cooker. Sorry for the bad news!