I don't what it's called, but just look at the image. Even in NWC2 it's impossible, because NWC2 doesn't allow invisible noteheads.
IMAGE:
http://img103.echo.cx/img103/2604/notes4br.gif
Please delete this thread.
Actually, NWC2 DOES allow invisible noteheads, and the effect shown IS possible in NWC2. In fact, it can be done in NWC1 with layering.
How can it be done in NWC1?
When you layer an open notehead with a closed notehead, it looks like a closed notehead.
If the quaver (eighth note) head is hidden, all the stems and the beam are invisible.
Instead of making it invisible, make it white (using a highlight color).
You can also offset either the first eighth or the half-note.