Private Sub Worksheet_Change(ByVal Target As Range)
 
    Dim lRow As Long
 
    On Error GoTo ErrorHandler
 
    'did the user change something in column C?
    If Not Intersect(Range("C:C"), Target) Is Nothing Then
 
        lRow = Target.Cells(1).Row
        Application.EnableEvents = False
 
        'did the user clear the cell in column C?
        If IsEmpty(Target.Cells(1)) Then
            Range(Cells(lRow, 1), Cells(lRow, 2)).ClearContents
 
        'only add info if column A is empty
        ElseIf IsEmpty(Cells(lRow, 1)) Then
            Cells(lRow, 1).Value = GetUserName
            Cells(lRow, 2).Value = VBA.Now
        End If
    End If
 
ErrorExit:
    Application.EnableEvents = True
    Exit Sub
 
ErrorHandler:
 
    Resume ErrorExit
End Sub