How do I modify serialized form data in jQuery?

I am trying to submit my form in AJAX, so I have to serialize() the data. But I am using fckEditor and jQuery doesn't know how to deal with it, so after the serialization, I am trying to manually modify the value, but no luck so far... any ideas

if(content_val!=""){
    var values = $("#frmblog").serialize();
    values.content = content_val; //content_val is the manually fetched data which I am trying to insert into the serialized content.
    alert(content_val); alert(values);
}