In the version 5.0, there is an JavaScript API which allows you paste HTML code into the editor.

 

This is an example:

 

function PasteHTML(html)
{
    // get the cute editor instance
    var editor1 = document.getElementById('<%=Editor1.ClientID%>');
    
    editor1.PasteHTML(html);
}

 

Hop it helps.

 

Let me know if you have any further questions.