说明：  三次贝塞尔分段插值(按照Excel曲线算法),计算平滑曲线上任意一点的点坐标的自定义函数BezierFit。 Excel的平滑曲线没有提供这个曲线图的公式，所以通过编程查找曲线上的点坐标。
(Cubic Bezier Interpolation (in accordance with the Excel curve algorithm) to calculate any point on a smooth curve point coordinates of the custom function BezierFit. Excel does not provide the smooth curve curve formula, so look through the programmed coordinates of points on the curve.)