The ability to change the href value of a hyperlink within a webpage can be easily done through javascript.
The A AHREF Link:
<a name="linkname" href="http://www.somesite.com/somepage.html">A Hyperlink</a>
After the webpage loads, javascript can be used to change the href value of "linkname" as shown below.
<script language="javascript" type="text/javascript">
<!--
var linkToChange_Name = "linkname";
var href_Path = "http://www.anothersite.com/somepage.html";
if (navigator.userAgent.toLowerCase().indexOf("msie") > -1) { /* Internet Explorer */
document.links(linkToChange_Name).href = href_Path;
}
else { /* Other */
document.links[linkToChange_Name].href = href_Path;
}
//-->
</script>