Private Sub Worksheet_Change(ByVal Target As Range)
    For Each cell In Target
        If cell <> "" Then
            If Not Intersect(cell, Range("C10:C10000")) Is Nothing Then
                With cell.Offset(0, -1)
                    .Value = Date
                   ' .EntireColumn.AutoFit
                End With
            End If
        End If
    Next cell
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)   
If Target.Count > 1 Then Exit Sub   
ActiveSheet.Unprotect   
Target.Locked = True   
ActiveSheet.Protect   
End Sub