How to dynamically switch stylesheet of editorarea?

The best way would be plugin with combo, I know how to do this, but how to change the stylesheet?

I have one idea, removeelement link with css style and use the FKCTools.AppendStyleSheet function, but how to get the document of editor area?

This could be the function of combo button

FCKDynamicCSSCommand.prototype.Execute = function(itemText, itemLabel) {
var list=document.getElementsByTagName("link");
for(i=0;list.length;i++) {
   var type=list[i].type;
   if (type="text/css") alert(list[i].href);
}

....       

but the problem is that the returned links are not in document of editorarea but its parent.

Does anyone know how to help me?

Thanks for effort...