C#

class SecondForm
{
   private TextBox tbText = new TextBox();
   
   public string TbText
   {
       get { return tbText.Text; }
       set { tbText.Text = value; }
   }
}

class MainForm
{
  SecondForm secondForm;

  public void ShowSecondForm()
  {
     secondForm = new SecondForm();
     secondForm.Show(); // or ShowDialog
  }

  public void SetText(string text)
  {
     secondForm.TbText = text;
  }
}

private int GetDoubleDigit(int var)
{
   int retVal = var;
   int length = var.ToString().Length; // Dunno if this will work for all cultures
   int n = length - 2;
   if (n > 0)
      retVal /= (int)Math.Pow(10, n);

   return retVal;
}

public static double Truncate(double value, double precision)
{
    double x = Math.Pow(10, precision);
    return (double)((int)(value * x)) / x;
}