InsertHtml is not a function

I'm obviously doing something wrong here, but I'm not quite sure what...I'm making a simple plugin. When someone clicks Ok from the little popup window, it's supposed to insert an id into the editor textarea. Whenever I click Ok, though, javascript error console yells at me and tells me that InsertHTML is not a function. Here's the relevant code:

var dialog = window.parent ;
var oEditor = dialog.InnerDialogLoaded();
var FCKLang = oEditor.FCKLang ;
var FCKVideoImages = oEditor.FCKVideoImages ;

...

function Ok()
{
   var video, image ;

   video = document.getElementById('video_id').value;
   image = document.getElementById('image_id').value;
   
   oEditor.InsertHtml(video);

   return true ;
}

Any ideas?