Fractured arm and comfrey (urgent) !!!!!!!!!!!!!!?

i fell of my horse and i have badly sprained my wrist and arm and i have broken the same arm before i have had xrays and there might be a small fracture the doctors said that they could but a cast on it or just leave it and wrap it up. there is no cast on it but my neighbour was saying that you an make comfrey leaves into a hard cast that drys. does this remedy help and does anyone know to make the comfrey cast.................