If you need to fire event from CKEDITOR when you type symbol in the edit zone:
CKEDITOR.replace('Body');
$(document).ready(function () {
CKEDITOR.instances['Body'].on('key', function () {
//Do something here.
alert('Symbol was typed');
});
});
The first bit replace standard textarea control with CKEDITOR (the name of the data field is "Body").
The second bit will fire event when somebody type a new symbol in editable area of the CKEDITOR.