Put different strings to label in modalpopwindow

Hi,
I have a modalpopwindow like this and 2 different linkbuttons. 
What I am trying to do is that Each of these linkbuttons will put a different string to label1 and a different Backgroundimage to panel2 in the modalpopwindow.
I have tried with the code below but no string or image is put to the controls when clicking either of the 2 linkbuttons. I think I have to do something more here ?
<asp:LinkButton ID="ShowPopup1" runat="server" Font-Size="10pt" ForeColor="White" onclick="ShowPopup1_Click">one</asp:LinkButton> <asp:LinkButton ID="ShowPopup2" runat="server" Font-Size="10pt" ForeColor="White" onclick="ShowPopup2_Click">two</asp:LinkButton> <asp:Panel ID="Panel1" runat="server" Width="645px" style="display:none;"> <as ...