Rendering action? and ffects alwasy apply to entire track?

I'm using the Pitch Shifter II and Vocal Transformer to apply to small segment of my audio. My audio is 2 tracks sent out from FCP 7 as a SoundTrack Pro Audio file (note I did not select Multi-Track).

I'll admit that I'm not a regular user of SoundTrack Pro so my knowledge is limited ... I'm primarily a Logic Pro person and haven't used SoundTrack Pro much at all.

What I'm trying to do is apply Vocal Transformer effect to a selected (segment of my audio) only, NOT the entire track. I can't seem to accomplish this? Whenever I setup the values I want to use in the Vocal Transformer, it applies them to the entire track regardless of what I have selected in the waveform display.

If I "Render to Action" I get the same results the entire audio track is render not just my selection.

I must be missing something basic, but how the heck to I have an Effect applied to just my selected audio segment and not the entire audio file? Or, does this HAVE to be Multi-track (FCP 7 Send To SoundTrack Pro Multi-track audio) in order to work the way I want it?

Thanks, Rob.