If you want to hear it through your monitors, it will always be travelling along the same path as anything else you're hearing.
If you don't need to hear it as you are recording, simply switch off the specific track output from the mixer window (I'm not exactly sure how Cubasis sets it up...I hope it's possible, I know for a fact you can do it in Cubase SX). This will let the sound come through on the inputs but you won't be able to hear it until you turn the track channel back on.
Also, you may need to fiddle with the mixer settings on the Emu; the output may be automatically blending the sound from your input as well as from the Cubasis output. If that's the case, there's NO way to turn it off without losing your input channel and recording nothing but silence.
I'm assuming you only have a pair of outputs to work with? Sometimes you can mess with the software routing and send a 'pre-mix' output to one pair and a 'post-mix' to another pair...if you can do that, then switching the output of the recording channel to the unused pair will work just fine (because you don't need to hear it, so it doesn't matter that nothing is connected).
I hope this is helpful. It kinda sounds like gibberish even to me, and I know what I'm trying to say.