If Dialog1.ListView1.Items.Count > 0 Then
 
		Dim d As New Date(1,1,1,0,0,0,0)
		Dim dstart As New Date(1,1,1,0,0,0,0)
		Dim s As Integer = 0
		Dim c As Integer = 0
		dim t as TimeSpan
 
      For i As Integer = 0 To Dialog1.ListView1.Items.Count - 2        
        Lines = Date.Parse(Dialog1.ListView1.Items(i).SubItems( _
          3).Text).ToString.Split(":")
        'wrt += Date.Parse("00:00:00").AddSeconds(Lines(2)).AddMinutes(Lines( 
        ' 1)).AddHours(Lines(0)).ToString()
        d=d.Add(New timespan(Lines(0),Lines(1),Lines(2)))
        c = c + 1
        Exit For
      Next
 
		s = datediff(dateinterval.Second,dstart,d) / c
		t = New TimeSpan(0,0,s) 
 
		debug.Print (t.Hours.ToString + ":" + t.Minutes.ToString + ":" + _
  t.Seconds.ToString)
 
    End If

Gruss mm78pr

http://msdn.microsoft.com/de-de/default.aspx