Sitemap menu with Description text

Question

In SP2010 publishing website, I have added the Description column in Pages library.

After that I created the menu with following code:

<PublishingNavigation:PortalSiteMapDataSource
    ID="SiteMapDS"
    runat="server"
    EnableViewState="false"
    SiteMapProvider="CurrentNavigation"
    StartFromCurrentNode="true"
    StartingNodeOffset="1"
    ShowStartingNode="false"
    TrimNonCurrentTypes="Heading"
/>

<SharePoint:AspMenu
    ID="CurrentNav"
    runat="server"
    EnableViewState="false"
    DataSourceID="SiteMapDS"
    UseSeparateCSS="false"
    UseSimpleRendering="true"
    Orientation="Horizontal"
    StaticDisplayLevels="1"
    MaximumDynamicDisplayLevels="1"
    CssClass="nightanday-menu"
    SkipLinkText="<%$Resources:cms,masterpages_skiplinktext%>"
/>

It renders the menu like:

BaseItem1 BaseItem2 BaseItem3
Item1A       Item2A       Item3A
Item1B       Item2B       Item3B

I am trying to fetch the description of each link and display it under the child items, something like:

BaseItem1                            BaseItem2                            BaseItem3

Item1A                                 Item2A                                 Item3A
a little description of 1A       a little description of 2A      a little description of 3A

Item1B                                 Item2B                                 Item3B
a little description of 1B       a little description of 2B      a little description of 3B

I tried something like:

<SharePoint:AspMenu
    ID="CurrentNav"
    runat="server"
    EnableViewState="false"
    DataSourceID="SiteMapDS"
    UseSeparateCSS="false"
    UseSimpleRendering="true"
    Orientation="Horizontal"
    StaticDisplayLevels="1"
    MaximumDynamicDisplayLevels="1"
    CssClass="nightanday-menu"
    SkipLinkText="<%$Resources:cms,masterpages_skiplinktext%>">
    <DynamicItemTemplate>
        <a href="<%#Eval('URL')%>"><%#Eval('Title')%></a>
        <br/>
        <small><%#Eval('Description')%></small>
    </DynamicItemTemplate>
</SharePoint:AspMenu>

But Eval(..) doesn't work here.

Is there a way to do it without making a custom webpart for the menu?

OR

Can I make changes to the DataSource and include Description column to it?