' Zeit-Differenz in Minuten
Dim nMin As Integer = TimeDiff("12:00:00", "16:44:33")
 
' Zeit-Differenz formatiert ausgeben
Dim sTime As String = New TimeSpan(0, nMin, 0).ToString.Substring(0, 5)
 
MsgBox(sTime)

Public Function TimeDiff(ByVal sTime1 As String, ByVal sTime2 As String) As _
  Integer
        ' Uhrzeiten in TimeSpan-Objekte überführen
        Dim time1 As TimeSpan = TimeSpan.Parse(sTime1)
        Dim time2 As TimeSpan = TimeSpan.Parse(sTime2)
 
        ' Zeitdifferenz in Minuten berechnen
        Dim nsec As Integer = 0
        With time2.Subtract(time1)
            nsec = .Hours * 3600 + .Minutes * 60 + .Seconds
 
            ' Falls negativ, 24 Stunden hinzuaddieren
            If nsec < 0 Then nsec += 24 * 3600
        End With
 
        Return (nsec)
    End Function
 
 
 ' Zeit-Differenz in Minuten
        Dim nsec As Integer = TimeDiff("12:00:00", "16:44:33")
 
        ' Zeit-Differenz formatiert ausgeben
        Dim sTime As String = New TimeSpan(0, 0, nsec).ToString
 
        MsgBox(sTime)

Dim nsec As Integer = TimeDiff(Label1.Text, MaskedTextBox.ToString)

Label4.Text = Format(Now, "HH:mm:ss")
 
        ' Zeit-Differenz in Minuten
        Dim nsec As Integer = TimeDiff(Label4.Text, TextBox2.Text)

 Dim nsec As Integer = TimeDiff(Label1.Text, MaskedTextBox.Text)