For all trendline types except moving average, sets or returns the point on the value axis where the trendline should intercept.

public double Intercept{ get; set; }
Public Property Intercept() As Double

If an intercept is not being used, this property will return Double.NaN. After setting this value, Trendline.UseIntercept will return true. To stop using an intercept value, use Trendline.ClearIntercept().