Order Property
Returns or sets the polynomial order for the specified trendline (an integer value greater than 1). If you set this property for a linear trendline, it becomes a polynomial trendline. Read/write Long.
expression.Order
expression Required. An expression that returns a ChTrendline object.
Example
This example sets the order for the specified trendline.
ChartSpace1.Charts(0).SeriesCollection(0).Trendlines(0).Order = 2