sometimes the menu html draws focus away from the textarea/contentEditable.
if that's the case, bind an event to each box, onfocus, which says "window.lastBox=this;".
you can then refer to the global variable lastBox, eg lastBox.value, lastBox.scrollTop, etc in your text injection code.
BROWSER STATS [% share]
(2013/10/31) IE7:0.5, IE8:8.6, IE9:5.3, IE10:12.3, FF:17.7, CH:41.8, SF:8.1, MOBILE:20.4