Num Lock gets off when opening the workbook

Hi there!

I've just added the following code to my workbook

Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target _
As Excel.Range)
If Target.Worksheet.Name = "2014" Then
    If Target.Column = 2 Or Target.Column = 5 Or Target.Column = 10 Or Target.Column = 11 Or Target.Column = 19 Or Target.Column = 30 Or Target.Column = 34 Then
    Application.SendKeys ("%{down}")
    End If
End If
End Sub

and when I open it, the num lock turns off. Any idea why?