I have this class and I need to add an alert in case inspStartTime.TimeID is greater than inspEndTime.TimeID

Each value represents a time e.g. 16:30 if inspStartTime.TimeID = 16:30 and inspEndTime.TimeID = 15.30 then throw exception.

Code:
         private bool EnumVisual(Visual myVisual)
        {
             InspectionTime inspStartTime;
             InspectionTime inspEndTime;
             
            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(myVisual); i++)
            {
                // Retrieve child visual at specified index value.
                Visual childVisual = (Visual)VisualTreeHelper.GetChild(myVisual, i);


                // Do processing of the child visual object.
                if (childVisual is TextBox)
                {
                    MaskedTextBox btn = (MaskedTextBox)childVisual;
                    //Check first to see if the element is null
                    if (btn.Tag != null)
                    {
                        //Check to see if it is the start time textbox i=on the screen
                        if (btn.Tag.ToString().ToLower()=="starttime")
                        {
                            //Fillthe inspection time data
                            inspStartTime = new InspectionTime();
                            inspStartTime.TimeID = Convert.ToInt32(btn.Uid);
                            inspStartTime.StartTime = btn.Text;

                            //Check to see if it is a valid time
                            if (IsValidTime(btn.Text))
                            {
                                //Update the starttime for the UID TimeID
                                if (timeManager.UpdateStartTime(inspStartTime, timeManager.GetJobIDViaTimeID(inspStartTime.TimeID)))
                                {
                                    saveedChanges = false;
                                    //Throw an exception to be handled
                                    throw new Exception("Invalid Time Entry");
                                }
                                else //If everything is ok make it so.
                                {
                                    btn.Background = System.Windows.Media.Brushes.White;
                                    saveedChanges = true;
                                }
                            }
                            else //The invalid time status entry
                            {
                                btn.Background = System.Windows.Media.Brushes.Red ;
                                saveedChanges =  false;
                                //Throw an exception to be handled
                                throw new Exception("Invalid Time Entry");
                            }

                        }
                        else if (btn.Tag.ToString().ToLower() == "endtime") //The textbox is the end time textbox
                        {
                            //Fillthe inspection time data
                            inspEndTime = new InspectionTime();
                            inspEndTime.TimeID = Convert.ToInt32(btn.Uid);
                            inspEndTime.EndTime  = btn.Text;

                            //Check to see if it is a valid time
                            if (IsValidTime(btn.Text))
                            {
                                //Do the update in the Database
                                if (timeManager.UpdateEndTime(inspEndTime, timeManager.GetJobIDViaTimeID(inspEndTime.TimeID)))
                                {
                                    saveedChanges = false;
                                    //Throw an exception to be handled
                                    throw new Exception("Invalid Time Entry");
                                }
                                else
                                {
                                    btn.Background = System.Windows.Media.Brushes.White;
                                    saveedChanges = true;
                                }
                            }
                            else
                            {
                                btn.Background = System.Windows.Media.Brushes.Red;
                                saveedChanges = false;
                                //Throw an exception to be handled
                                throw new Exception("Invalid Time Entry");
                            }
                        }

                    }
                   
                }

                // Enumerate children of the child visual object.
                EnumVisual(childVisual);
            }

            return saveedChanges;

        }