automatic logging of changes to spreadsheet?

Public RAGenabled As Boolean
Dim OldVal As String
Private Const lDelim As String = "("
Private Const rDelim As String = ")"

Private Sub cbRAGenabled_Click() 
' A checkbox on the worksheet  that controls whether the auditing is done or not
    RAGenabled = cbRAGenabled.Value
    If RAGenabled = True Then
        MsgBox "RAG checking enabled"
    Else
        MsgBox "RAG checking disabled"
    End If
End Sub

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
'
' Determines whether the range (cell) that was changes is one I want to audit (and only if auditing is ON)
'
    If RAGenabled = True Then   'Only bother if RAG checking is toggled ON
        Application.EnableEvents = False  ' prevent recursive worksheet_change events
        If Not (Application.Intersect(Target, Range("MyRange")) Is Nothing) Then ' Process if selection is in MyRange range
            Call AuditTheChange(ByVal Target)
        End If
        ' If selection is not in MyRange ranges, ignore it
        Application.EnableEvents = True ' re-enable events
    End If
'
End Sub

Private Sub Worksheet_SelectionChange(ByVal Target As Excel.Range)
'
    RAGenabled = cbRAGenabled.Value 'ensure current value, esp. first time through
    If RAGenabled = True Then   'Only check if RAG checking is toggled ON
        If (Application.Intersect(Target, Range("MyRange")) Is Nothing) Then ' is it in MyRange?
            'MsgBox "Selected cell is not within an appropriate range"    ' For debugging purposes only
            Exit Sub 'if it's not in a range to be audited, do nowt
        Else 'it is, so ...
            If Target.Count = 1 Then ' is only one cell selected?
                OldVal = Target.Value
                'MsgBox "OldVal='" & OldVal & "'"   ' For debugging purposes only
            Else
                MsgBox "Multiple selections can't be processed - select one cell at a time"
            End If
        End If
    End If
'
End Sub

'The cell value is stored in a public variable when a cell is selected (Worksheet_SelectionChange procedure).
'Then, when a new value is added, the Worksheet_Change event procedure adds a cell comment
'(the error generated if the cell already has a comment is stepped over) and then uses the stored variable
'as part of the text string for the comment, building up a change history over time.
'Adapted from http://www.j-walk.com/ss/excel/eee/eee014.txt

Sub AuditTheChange(ByVal Target As Range)
'
    If Target.Count = 1 Then ' check is only one cell selected?
        ' record a change in a comment box
        On Error Resume Next    ' Ignore the error if you have previously ....
        Target.AddComment       ' added comment box
        Target.Comment.Text Target.Comment.Text & "Whatever you want the audit text to be"
        Target.Interior.Pattern = xlSolid
        With Target.Font
             .Name = "Arial" 
             .Size = 10
             .Strikethrough = False
             .Superscript = False
             .Subscript = False
             .OutlineFont = False
             .Shadow = False
             .Underline = xlUnderlineStyleNone
             .ColorIndex = xlAutomatic
        End With
        OldVal = Target.Value    ' reset OldVal in case the selection is not changed before the cell value is changed again                      
    End If
End Sub