Change Title of Sitemap through code.. not working

HI,
i have a sitemap and i want to update through code behind,,
but its now working,, please help me to correct this

<?xml version="1.0" encoding="utf-8" ?>
<siteMap xmlns="http://schemas.microsoft.com/AspNet/SiteMap-File-1.0" >
    <siteMapNode url="Applied Leaves status.aspx" title="Leaves"  description="">
        <siteMapNode url="Db_Operation.aspx" title="apply Leaves"  description="" />
        <siteMapNode url="" title="1" description="" />
    </siteMapNode>
</siteMap>

Sorry,, Code is as follows

  Dim currentNode As SiteMapNode = SiteMap.CurrentNode

        For Each ChildNodesEnumerator As SiteMapNode In SiteMap.CurrentNode.ChildNodes
            ' Displays the title of each node.
            ChildNodesEnumerator.Title = "Server"
        Next