How long would it take to switch from being right-handed to left-handed?

Left handed nature: At one time children would be forced to switch from left handedness to right handedness through persistent exercises and use of the right hand rather than the left. Since the left handedness arises from one's neurologic makeup, it will always be dominant, but one can learn right handed uses through persistence and exercise. To my knowledge, one is not really converted to the right handed nature.