Dynamically load ckeditor and doc in iframe

I have an html file that includes CKEditor.replace and I load it into an iframe when the frameset loads: This works fine. I can then load data into the editor like so:

var iframe = document.getElementById('editFrame')
myEditor=iframe.contentWindow['CKeditor1'];
myEditor.insertHtml(data);

I now want to dynamically load the iframe like so:

iframe.src="ckeditor/myFile.html";
myEditor=iframe.contentWindow['CKeditor1'];
myEditor.insertHtml(data);

The iframe loads with the editor, but the insertHtml fails. I think it's because the code runs before the edtior has finished loading.

In the same function, how can I accomplish loading the page containing the editor and insert data into the editor?