Public Declare Function GetKeyState Lib "user32" _
  (ByVal nVirtKey As Long) As Integer

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    If Target.Column = 9 Then        'Spaltennummer für "I"
        If GetKeyState(vbKeyTab) < 0 Then
            Target.Offset(0, -1).Activate          'Oder was Du hier halt 
            ' brauchst
        End If
    End If
End Sub