Under no circumstances may one interrupt his S”E to say Kedusha, UNLESS he is holding in the place where Kedusha should actually be said [i.e., he just finished the second bracha of the Amidah], or he is holding in Elokai Netzor (in the latter case, he should interrupt to answer “Kadosh” and “Baruch” and, according to SOME opinions, also “Yimloch”).
See here regarding skipping: http://www.theyeshivaworld.com/news/headlines-breaking-stories/257544/halachically-speaking-tefilla-btzibur.html