OnClientClick + delete files

Hi all,
im want some help, i need to delete some files with OnClientClick command.
Have a look:
<asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="False"
                            CommandName="Update" Text=" ????????? " BackColor="#FF9900"
                            Font-Bold="True" Font-Size="Large" Font-Underline="False" OnClientClick="koukou()" />


code behide:
Protected Sub koukou()
        File.Delete(uploadFolder & "file-1.jpg")

        ...