private void button3_Click_1(object sender, EventArgs e)
        {
            foreach (Form f in this.MdiChildren)
            {
                if (f.GetType() == typeof(CHECKBILL_PRINT))
                {
                    f.Activate();
                    return;
                }
            }
            Form room = new CHECKBILL_PRINT();

            room.MdiParent = this;
            room.Show();
        }
        private void sPILTBILLToolStripMenuItem_Click(object sender, EventArgs e)
        {
            foreach (Form f in this.MdiChildren)
            {
                if (f.GetType() == typeof(CHECKBILL_PRINT))
                {
                    f.Activate();
                    return;
                }
            }
            Form cal = new CHECKBILL_PRINT();

            cal.MdiParent = this;
            cal.Show();
        }