frm = new Form();
           frm.Owner = MainForm;
           frm.StartPosition = FormStartPosition.Manual;
           frm.Width = this.PullDownWidth;
           frm.Height = this.PullDownHeight;

            int x = 0;
            int y = 0;

            x += MainForm.Location.X;
            x += textbox.Location.X;
            x += textbox.Height;

            y += MainForm.Location.Y;
            y += textbox.Location.Y;

            frm.Location = new Point(x, y);
            frm.Show();