Asp .net menu same node selected by more than one file

I would like to be able to select one node in a menu with more than one file.
Lets say I have a menu with two nodes, details and contact.
Detail node points to details.aspx and contact node points to contact.aspx.
I now have a third page called DetailPreview.aspx.
You can get to this page from a link in the detail.aspx.
I want the detail menu node to be selected once I get to DetailPreview.aspx.
I don't want to use server.transfer when I go from Detail.aspx to DetailPreview.aspx.
I dont want anothe node pointing to the detailpreview.aspx
           
Any solution????
^Thanks

This is my Sitemap:
<?xml version="1.0" encoding="utf-8" ?>
<siteMap xmlns="http://schemas.microsoft.com/AspNet/SiteMap-File-1.0" >
  <siteMapNode url="~/Default.aspx" title="Home">
    <siteMapNode url="~/Details.aspx" title="Details" />
    <siteMapNode url="~/ContactUs.aspx" title="Contact Us" />
  </siteMapNode>
</siteMap>
and my menu:
<asp:Menu ID="MainMenu" runat="server" Orientation="Horizontal" MaximumDynamicDisplayLevels="2"
                DataSourceID="SiteMapDataSource1" DynamicEnableDefaultPopOutImage="False" StaticEnableDefaultPopOutImage="False">
                <StaticMenuStyle CssClass="menu" />
                <StaticMenuItemStyle CssClass="menuItem" />
                <StaticSelectedStyle CssClass="menuSelectedItem" />
                <DynamicMenuStyle CssClass="menuPopup" />
                <DynamicMenuItemStyle CssClass="menuPopupItem" Font-Strikeout="False" />
                <DynamicHoverStyle CssClass="menuPopupItem" />
                <StaticHoverStyle CssClass="menuItemHover" />
            </asp:Menu>

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