private void buttonItem1_Click(object sender, EventArgs e)
 {
     FrmTienMat frmTienMat = new FrmTienMat();
     frmTienMat.Show();
 }
        private void buttonItem1_Click(object sender, EventArgs e)
        {
            FrmTienMat frmTienMat = new FrmTienMat();

            frmTienMat.Show();
        }