I'm uber confused with this question. There isn't any difference between sending one channel, two channels, or 30 channels to an FX channel. Of course, using sends will always raise the volume, since you're keeping the "dry" sound but adding "wet" on top of it - but it doesn't make any difference how many channels are routed to it.

Are you trying to say that you want to add some sends/FX channels and lower the volume of the rest of the track to maintain the same peak volume? If so, then no, there is no way to do that except by using your ears and the meters; Cubase couldn't possibly do it for you because the FX channel may not necessarily have a constant gain (in fact it almost certainly doesn't). But then, your FX channel is going to be routed straight to the master anyway, and this is really what mastering compressors/levellers are for...

___________________
My party schedule:
2009-02-21 - DJ Attention @ I'm So Popular
2009-06-18 - DJ Annoying @ People Need To Know Where I'll Be
2012-11-32 - DJ Insufferable ɸ Or At Least the Stalkers I Complain About
2048-06-66 - Spastic & Whocares ¶ Although I'm Actually Flattered
9999-45-81 - Tweaker Gimp ☼ I Probably Won't Even Go To This But I Have To Make Sure I Fill Up All The Available Space Here

yea thats what i meant. didn't really think of it like that....

kind of disapointing really but makes sense

___________________

Well, I suppose one shortcut would be just to bounce the FX track and check its peak/RMS/etc. in Wavelab (or whatever your audio editor is, you could use Cubase too). Would probably take about 30 seconds and you'd know exactly how much to lower the volume.

Still, it's probably better to use your ear - I think if you did it the way above, you'd end up quieter than you really want to be, especially if it's a reverb effect for example.

___________________
My party schedule:
2009-02-21 - DJ Attention @ I'm So Popular
2009-06-18 - DJ Annoying @ People Need To Know Where I'll Be
2012-11-32 - DJ Insufferable ɸ Or At Least the Stalkers I Complain About
2048-06-66 - Spastic & Whocares ¶ Although I'm Actually Flattered
9999-45-81 - Tweaker Gimp ☼ I Probably Won't Even Go To This But I Have To Make Sure I Fill Up All The Available Space Here

Dude I know exactly what you mean

You have to turn down the volume of the fx track by -6dB


Then, turn the MIX of your effect to 100%%%% so that the only signal that comes from the fx track is only the one created by the effect and not the original audio.