Amen!
I’ve never tried this method, but here’s a video that may be helpful:
http://dl.dropbox.com/u/8520185/c6_tcsync_with_timewarp.swf
BTW, this is NOT my video. It’s from another thread, which unfortunately I cannot find, where someone was asking a similar question (and I kept it just in case I would need this in the near future). In short, in the video he shows two cues that have already been locked, except now there’s a need to make tempo changes in between them without changing their timecode. The way he goes about it is by creating two reference tracks (labeled ‘#TIME’ and ‘#MUSIC’) onto which he inserted clip events in the first bar of each cue. Notice that the #TIME track is set to linear mode (and it is locked) while the #MUSIC track is set to musical mode (unlocked). The #TIME track is being used as the event that defines where the music should be after the tempo changes have been made.
Alright, so now you have your reference events and you proceed to make the tempo changes, which would obviously have moved the #MUSIC track. In order to get it back to where it was in the timecode, he uses the Replace Bars function of the Process Bars utility in Cubase. This way he can change the Time Signature of a single bar without affecting the rest of the track. By doing this, you can get the music closer to it’s original location before using the Timewarp tool. He leaves the latter for fine adjustments. BUT, make sure you make a note of the original tempo of the second cue (as seen 0:36 secs into the video). Otherwise, your second cue will be out of sync due to the tempo change that the Timewarp tool creates. Just dial back the original tempo of the second cue and it should all line up correctly. That’s pretty much the whole process (as if 
).
I wished there was an easier way to do this in Cubase, like you can in Digital Performer. That would be awesome!
HTH