Ok, I'll insert a track into my Nero 6 SE (works like the full, not the Express)
It's in the compilation window, as track 1
Rightclick, and select PROPERTIES ... never realized that alt-Enter was a shortcut for that.
Change the pause to 0 first, otherwise all the splits will have a 2 second pause as well.
Select the "Indexes, Limits, Split" tab at the top of the popup display, you should see a an audio waveform view, where you can judge the quiet positions by eye, you can also zoom in, and play segments etc.
Mark the postion with the mouse, then hit the SPLIT button - you can move the inserted split with the mouse. After placing as many splits as you want, when you ok it, the track will be divided in the compilation window.
Seems to work the same way in Nero Express view as well.