You can use the SiteMap control and page to accomplish this,
First create a Sitemap page and add the navigation paths,
<?xml version="1.0" encoding="utf-8" ?>
<siteMap xmlns="http://schemas.microsoft.com/AspNet/SiteMap-File-1.0" >
<siteMapNode url="A1.aspx" title="Select Category" description="">
<siteMapNode url="A2.aspx" title="Select Sub Page" description="" >
<siteMapNode url="A.aspx" title="Page A" description="" />
<siteMapNode url="B.aspx" title="Page B" description="" />
<siteMapNode url="C.aspx" title="Page C" description="" />
<siteMapNode url="D.aspx" title="Page D" description="" />
<siteMapNode url="E.aspx" title="Page E" description="" />
</siteMapNode>
</siteMapNode>
</siteMap>
Then add the Sitemap control to your master page,
<asp:SiteMapPath ID="SiteMapPath1" runat="server" ShowToolTips="false" />