Stefan,
thanks for the reply. I understand to add or modify the bookmarked paragraph only at its end, but if I have to add a new chapter or paragraph before the bookmarked one... this is another problem, since the reference points again to the same X.X.X heading and don't increment its bookmark accordingly to the new Y.Y.Y heading... this is my main problem, due to I'm editing manuals with numbered headings and sometimes happens that I have to insert new paragraphs and so the next cross-references should update its reference accordingly... so in my case you mean that I shouldn't use cross-reference at all?!? Maybe in future MS will fix this thing? Perhaps with Word 2013???

Thanks again for your prompt reply