check out this thread:
http://www.lucasforums.com/showthrea...hlight=resrefs
Basically you want to find an exising vo resref of a twilek dialogue and place that file name in the vo_resref in dlgeditor for your own twilek converstation.
EDIT:
for example from TSL from 304NAR_dlg.erf...twilkedo.dlg...voresref is 304twilekdo001...put this file name in the VO_ResRef box for your twilek part of the conversation. Off hand, I don't know if this is a male or female voice, prob male.