private void Form1_SizeChanged(object sender, EventArgs e)
        {
            //запомнить высоту и ширину главного окна в переменную и потом как то применить?
            MainForm.He = this.Height; 
            MainForm.Wi = this.Width;
        }

  private void Form_Export_SizeChanged(object sender, EventArgs e)
        {
           He = this.Height;
           Wi = this.Width;
           int len = this.MdiChildren.GetLength(0);
            for (int i = 0; i < len; i++)
            {
                if (this.MdiChildren[i].Name == "Logs")
                {
                    MdiChildren[i].Location = new Point(0, MainForm.Wi);
                    MdiChildren[i].Height = MainForm.He / 4;
                    MdiChildren[i].Width = MainForm.Wi - 20;
                }
            }
            }