how do i append to xml files

[abehm]

Hi,
I have a method that inserts class data into a new xml document, however I would like to append the data after the last element of an existing xml document.

here is the code I have:
if anyone can offer any help or suggestions, that would be appreciated.

[CODE=c]public string Insert(string XMLFile)
{
string XMLDirectory = this.xmlDir + this.ProjectorS N + @"\";
string file = XMLDirectory + XMLFile;
System.Xml.XmlT extWriter writer;

if (!System.IO.Dir ectory.Exists(X MLDirectory))
{
System.IO.Direc tory.CreateDire ctory(XMLDirect ory);
}

writer = new System.Xml.XmlT extWriter(file, System.Text.Enc oding.UTF8);
writer.Formatti ng = System.Xml.Form atting.Indented ;
writer.WriteSta rtDocument();
writer.WriteSta rtElement("Prod uctTest");

writer.WriteEle mentString("Pro ductSN", this.ProjectorS N);
writer.WriteEle mentString("Pac kageID", this.LightEngin eSN);
writer.WriteEle mentString("Par t2", this.Lamp1);
writer.WriteEle mentString("Par t3", this.Lamp2);
writer.WriteEle mentString("Dat eTime", this.DateTime);

writer.WriteWhi tespace(" ");
// Write End of root element
writer.WriteEnd Element();

// Write End of document
writer.WriteEnd Document();

writer.Close();

return (XMLDirectory + XMLFile + " saved.");
}[/CODE]