ArgumentOutOFRangeException when comparing times - vb.net

Question

I'm working on a simple project to use at work (logistics company) for my colleagues and me.
Let me explain a little to make my question a bit easier.
Each Route represents a country that has a deadline. In this example I use Route 114. Route 114 represents the Netherlands and the orders should be finished at xx:xx:xx local time.
I'm using a DateTimePicker so the user can select the deadline and receive a warning if the ProgressBar reaches 70% (in this case a label turns red).
The code I have works so far, but sometimes it throws out an error saying:
Value of '-4758' is not valid for 'Maximum'. 'Maximum' must be greater
than or equal to 0. Parameter name: Maximum
I'm an amateur, but it looks like the time is counting backwards in some cases and thus results in a negative Value.
Public Class Deadlines
Private Route114Deadline As Boolean = False
Public Function GetTimeDifference(ByVal EndTime As DateTime, ByVal StartTime As DateTime) As Integer
Dim span As TimeSpan = EndTime.TimeOfDay - StartTime.TimeOfDay
Dim result As Integer = CInt(span.TotalSeconds)
Return result
End Function
Private Sub tm114_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tm114.Tick
' ROUTE 114 '
Dim value114 As Integer = pb114.Maximum - GetTimeDifference(DateTimePicker1.Value, DateTime.Now)
If value114 > pb114.Maximum Then
tm114.Stop()
End If
If value114 < pb114.Minimum Then
tm114.Stop()
Exit Sub
End If
pb114.Value = value114
If Not Route114Deadline AndAlso pb114.Value >= pb114.Maximum * 0.7 Then
Route114Deadline = True
lb114.ForeColor = Color.Red
End If
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
pb114.Minimum = 0
pb114.Maximum = GetTimeDifference(DateTimePicker1.Value, DateTime.Now)
tm114.Start()
End Sub
End Class

Answer 1

Found the solution with some help!
Public Class Form1
Private Route114Deadline As Boolean = False
Public Function GetTimeDifference(ByVal EndTime As DateTime, ByVal StartTime As DateTime) As Integer
Dim span As TimeSpan = EndTime - StartTime
Dim result As Integer = CInt(span.TotalSeconds)
Return result
End Function
Private Sub tm114_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tm114.Tick
' ROUTE 114 '
'get the seconds from now to end
Dim value114 As Integer = GetTimeDifference(DateTimePicker1.Value, DateTime.Now)
'check if the seconds are less than 0
If value114 < 0 Then
tm114.Stop() 'stop the timer
pb114.Value = 0 'set the progressbar to 0 just in case the last value was 1 second and is now less than 1
MessageBox.Show("Time for (114) is up!!!") 'show a message or change the text of a label to allert that time is up
Exit Sub
End If
pb114.Value = value114 'set the progressbar to new amount of seconds
If Not Route114Deadline AndAlso pb114.Value <= pb114.Maximum * 0.7 Then
Route114Deadline = True
lb114.ForeColor = Color.Red
End If
End Sub
Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
'get the number of seconds from now to end
Dim secs As Integer = GetTimeDifference(DateTimePicker1.Value, DateTime.Now)
'make sure there is at least 1 second before setting the progressbar maximum and starting the timer
If secs > 0 Then
pb114.Maximum = secs
tm114.Interval = 500
tm114.Start()
Else
MessageBox.Show("The chosen deadline time has already passed")
End If
End Sub
End Class