private static double GetNextSlope(int index, int count, List <DateValue> values, DateValue dv) { double nextSlope = 0; if (index < count - 1) { DateValue dv2 = values[index + 1]; nextSlope = (dv2.Value - dv.Value) / (dv2.Date.ToOADate() - dv.Date.ToOADate()); } return(nextSlope); }