/*  Timer elapsed definitions  */
        private void Timer_loopRegister_Elapsed(object sender, EventArgs e)
        {
            if (ProgramData.LoginSuccess)
            {
                if (radio_register.Checked)
                {
                    string opcode = ProgramData.ReadyToSelectCoursesList[ProgramData.CurrentSelectCourseIdx].ToString();

                    HttpCommunication.AddRegister(opcode, out string msg);

                    if (ProgramData.CurrentSelectCourseIdx + 1 == ProgramData.ReadyToSelectCoursesList.Count)
                    {
                        _timerLoopRegister.Stop();

                        btn_readySelCoursesList.Enabled = true;
                        radio_register.Enabled          = radio_selection.Enabled = true;
                        checkBox_OnSchedule.Enabled     = true;
                        group_TimePicker.Enabled        = checkBox_OnSchedule.Checked;

                        btn_StartReg.Enabled = true;
                    }
                    else
                    {
                        ProgramData.CurrentSelectCourseIdx += 1;
                    }

                    AddLog(msg);
                }
            }
        }