Private Sub Worksheet_Change(ByVal Target As Excel.Range)
For Each cell In Target
With cell
On Error Resume Next
OldText = .Comment.Text
If Err <> 0 Then .AddComment
MsgBox OldText & "Changed by " & Application.UserName & " at " & Now & vbLf
.Comment.Text NewText
.Comment.Visible = True
.Comment.Shape.Select
Selection.AutoSize = True
.Comment.Visible = False
End With
Next cell
End Sub