Prueba y comenta
Private Sub Worksheet_Change(ByVal Target As Range)
On Error GoTo ErrorHandler
If Target.Cells.Count = 1 And Not Intersect(Target, Me.Columns("A")) Is Nothing Then
Application.EnableEvents = False
If Len(Target.Value) > 0 Then
Target.Value = Left(Target.Value, 8)
Me.Range("A9").Select
End If
End If
ErrorHandler:
Application.EnableEvents = True ' Reactiva eventos pase lo que pase
End Sub