Plugin with own xml-tag

Hi there!

I am trying to implement a new plugin.
The plugin should only insert a new xml-construct like

<media type="video">
    <param name="url">video/video1.avi</param>
</media>

My site is using this xml to load the related player and sources... this works well... now i want to create a plugin which you can edit this media-tag.
Does anybody dealt with something like that before and/or having any hints and tipps?

First i want to display the xml with my own image, according to the flash-function... but i'm going crazy...
I tried a lot of things, but nothing works...

according to the placeholder-plugin, i tried something like:

FCKXHtml.TagProcessors['media'] = function( node, htmlNode )
{   
   if ( htmlNode.url )      
      node = FCKXHtml.XML.createTextNode( '[[' + htmlNode.url+ ']]' ) ;
   else
      FCKXHtml._AppendChildNodes( node, htmlNode, false ) ;

   return node ;
}

didnt work...
then i tried something like:

var FCKMediaProcessor = new Object();
FCKMediaProcessor.ProcessDocument = function(A)
{
   var B = A.getElementsByTagName('MEDIA');
   var C;
   var i = B.length - 1;
   while (i >= 0 && (C = B[i--]))
   {
      var D = C.cloneNode(true);
      D.setAttribute('load', C.getAttribute('url'));
      var E = FCKDocumentProcessors_CreateFakeImage('FCK__MYMEDIA', D);
      E.setAttribute('_fckmymedia', 'true', 0);
      
      FCKMediaProcessor.RefreshView(E, C);
      
      C.parentNode.insertBefore(E, C);
      
      C.parentNode.removeChild(C);
   };
};

FCKMediaProcessor.RefreshView = function(A, B)
{
   if (B.width > 0)
   A.style.width = FCKTools.ConvertHtmlSizeToStyle(B.width);
   if (B.height > 0)
   A.style.height = FCKTools.ConvertHtmlSizeToStyle(B.height);
};
FCKDocumentProcessor.addItem(FCKMediaProcessor );

but, there is a JS-Error: FCKDocumentProcessor.addItem is not a function...

Please help...