private void cmdEnableUser_Click(object sender, EventArgs e)
        {
            int     vEnrollNumber;
            int     vEMachineNumber;
            int     vFingerNumber;
            Boolean vRet;
            int     vFlag;
            int     vErrorCode = 0;

            lblMessage.Text = "Working...";
            Application.DoEvents();

            vEMachineNumber = cmbEMachineNumber.SelectedIndex + 1;
            vEnrollNumber   = Convert.ToInt32(txtEnrollNumber.Text == "" ? "0" : txtEnrollNumber.Text);
            vFingerNumber   = Convert.ToInt32(cmbBackupNumber.Text);
            vFlag           = chkEnable.Checked ? 1 : 0;

            vRet = bpc.EnableDevice(Program.gMachineNumber, 0); // 0 : false
            if (!vRet)
            {
                lblMessage.Text = util.gstrNoDevice;
                return;
            }

            vRet = bpc.EnableUser(Program.gMachineNumber, vEnrollNumber, vEMachineNumber, vFingerNumber, vFlag);
            if (vRet)
            {
                lblMessage.Text = "Success!";
            }
            else
            {
                bpc.GetLastError(ref vErrorCode);
                lblMessage.Text = util.ErrorPrint(vErrorCode);
            }

            bpc.EnableDevice(Program.gMachineNumber, 1); // 1 : true
        }