Closer, but it seems to me, if you want a 1ms burst of 120Khz, you'll probably want lot's of them, and most likely timed with a Zero-crossing reference.

Which if true, means you're trying to do X-10 stuff.

Which if true, you might want to look at this thread ...

XOUT and HPWM
http://www.picbasic.co.uk/forum/showthread.php?p=20318

Yes, I've just given you a sharp sword, with which to commit sepuku ... (a.k.a. Hari-Kari).