append data in xml file

<?xml version="1.0" encoding="UTF-8"?>

<company name="Macromedia">
<location name="Newton">
  <employees>
          <person>Demi Moore</person>
          <person>Bruce Willis</person>
  </employees>
</location>
<location name="San Francisco">
   <employees>
     <person>Tom Cruise</person>
     <person>Ben Forta</person>
     <person>Nicole Kidman</person>
   </employees>
</location>
</company>

I want to append another "location" node. without write xml file..

It would be like this...

<?xml version="1.0" encoding="UTF-8"?>

<company name="Macromedia">
<location name="Newton">
   <employees>
           <person>Demi Moore</person>
           <person>Bruce Willis</person>
   </employees>
</location>
<location name="San Francisco">
    <employees>
      <person>Tom Cruise</person>
      <person>Ben Forta</person>
      <person>Nicole Kidman</person>
    </employees>
</location>

<location name="New Location">
    <employees>
      <person>Prasun</person>
      <person>Mitra</person>
      <person>Pinku</person>
    </employees>
</location>
</company>

Please help me....

Thanks & Regards