When the chazzan starts kedusha in chazarat hashatz while you're davening, are you supposed to answer the chant, continue in your tefilla, or just not say anything?
אינו פוסק לא לקדיש ולא לקדשה אלא ישתק ויכון למה שאומר שליח-צבור ויהא כעונה א"ח קד:ז
One who is still reciting the Shemoneh Esrei (i.e. has not concluded Sim Shalom/Shalom Rav) should not respond to the shliach tzibur but should pause and listen quietly (Shulchan Aruch Orach Chaim 104:7).
If one has concluded the Shemoneh Esrei proper but is still reciting the concluding tefillos customary to say during the silent Shemoneh Esrei see O.C. 122:1
If you reach the end of Mechaye Meisim at the same time that the shaliach tzibbur begins kedusha, you answer kedusha (Shulchan aruch O.C. 109:2)