Try something like this out...
Private Sub TrackBar1_Scroll(sender As Object, e As EventArgs) Handles TrackBar1.Scroll
Dim bar As TrackBar = DirectCast(sender, TrackBar)
Select Case bar.Value
Case Is >= 1000
bar.SmallChange = 1000
Case Is > 100
bar.SmallChange = 50
Case Is > 50
bar.SmallChange = 50
Case Is > 25
bar.SmallChange = 25
Case Is > 10
bar.SmallChange = 15
End Select
Dim discrete As Integer = TrackBar1.Value \ TrackBar1.SmallChange
Dim Value As Integer = discrete * bar.SmallChange
bar.Value = Math.Min(Math.Max(bar.Minimum, Value), bar.Maximum)
Label4.Text = IIf(bar.Value >= 1000, bar.Value \ 1000, bar.Value) & IIf(bar.Value >= 1000, "s", "ms")
End Sub