/// <summary>
/// point 3 z2 value changed
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void DistanceCalculationZ2Changed(object sender, EventArgs e)
{
Point3d a = new Point3d(Double.Parse(X1.Text), Double.Parse(Y1.Text), Double.Parse(Z1.Text));
Point3d b = new Point3d(Double.Parse(X2.Text), Double.Parse(Y2.Text), Double.Parse(Z2.Text));
totalDist.Text = a.DistanceBetween(a, b).ToString();
}