<!DOCTYPE html>
<html>
<body>
<div id="editor" oncopy="copy(event)" onpaste="paste(event)" contenteditable>some text</div>
<script>

var HTMLToCopy = null;
var didCopy = false;
var didPaste = false;

function copy(event) {
    if (HTMLToCopy) {
        event.clipboardData.setData('text/html', HTMLToCopy);
        event.preventDefault();
    }
    didCopy = true;
}

function paste(event) {
    pastedHTML = event.clipboardData.getData('text/html');
    didPaste = true;
}

editor.focus();
</script>
</body>
</html>