public void ShowMdi(string frmName)
        {
            foreach (Form mdiFrm in this.MdiChildren)
            {
                if (mdiFrm.GetType().Name == frmName)
                {
                    mdiFrm.Activate();
                    mdiFrm.BringToFront();
                    return;
                }
            }

            Form frm = null;
            switch (frmName)
            {
                case "InputCodeFrm":
                    frm = new InputCodeFrm();
                    break;
                case "WeightFrm":
                    frm = new WeightFrm();
                    break;
            }
            if (frm != null)
            {
                frm.MdiParent = this;
                frm.WindowState = FormWindowState.Maximized;
                frm.Show();
            }
        }

        private void toolStripButton2_Click(object sender, EventArgs e)
        {
            ShowMdi("InputCodeFrm");
        }

        private void toolStripButton3_Click(object sender, EventArgs e)
        {
            ShowMdi("WeightFrm");