As of right now I believe there is only a method available that uses the NodeGuid. The result set should return the NodeParentID in which you could create a simple function in code behind to get the URL for the parent node or the NodeAilasPath based on the NodeParentID. Shouldn't be much code at all. You could even put it in your Transformation. Here is some code that should work
<script runat="server">
protected string GetParentUrl(int parentNodeId)
{
string returnurl = "#";
CMS.DocumentEngine.TreeProvider tree = new CMS.DocumentEngine.TreeProvider();
CMS.DocumentEngine.TreeNode tn = tree.SelectSingleNode(parentNodeId);
if (tn != null)
{
returnurl = tn.NodeAliasPath;
}
return returnurl;
}
</script>
Then in your code you provided simply do
href="<%# GetParentUrl(EvalInteger("NodeParentID")) %>"