[rpmccormick]

I don't think there is a way to do that unfortunately.

I use AC's S2U2's volume control shown in the pic (you have to enable volume, transparency, and keyboard-hook in S2U2 setup)

His works the same as the default dialer. However, since his works by hooking the volume keypress, I'm sure he could easily make it work how you like. You would probably have better luck trying to get him to add your request as a future feature than finding a way to hack the default one (I could be wrong though). I too would probably change the key-volume-step to 1 or 2 instead of the current 3 steps if the feature was there.