With Range('A1')
If .Comment Is Nothing Then
.AddComment
.Comment.Text Text:='@+Thierry' & Chr(10) & 'Created on : ' & Format(Now, 'DD/MM/YY HH:MM:SS') & _
' By Thierry', Start:=Len(.Comment.Text) + 1, OverWrite:=False
Else
.Comment.Text Text:=Chr(10) & 'Reviewed on : ' & Format(Now, 'DD/MM/YY HH:MM:SS') & _
' by ' & Application.UserName, Start:=Len(.Comment.Text) + 1, OverWrite:=False
End If
(etc.)