Hi Harry
It is actually quite easy to use the scroll wheel to move the views up and down. I have been doing that for ever since I started playing CMBO and now CMBB.
I use a Mac Powerbook 400G3 with a Kensington 2 button /scrollwheel mouse and a shareware control panel called "USB overdrive" which allows me to map my mouse function to any keystroke or action. I am sure there must be equivalents in the PC world.
The key (sorry about the pun) is that the + and - keys on the number keypad of the keyboard are shortcuts to move up or down a level. Just map your scroll up to eqaul a keypress of + on the number keypad section of the keyboard and scroll down to the - key. I have also mapped my right button to be equivalent to pressing the shift key and so I can scroll view right or left by prsseing right button and moving the mouse to the side of the screen. I realise that in CMBB side scrolling is possible on the lower third of the side of the screen but I still find this useful.
The other function I have mapped is by click pressing my scroll wheel and scrolling at the wheel, I use that as camera dip up or down.
You could probably work out the best combination for you,eg mapping click scroll to zoom/unzoom. I tend to use a combination of keyboard and mouse when I play and so I always have one hand on the key board using the keyboard shortcuts to move, hunt, target, etc...etc..., therfore I also use ths control click method to jump quicly from spot to spot on the map.
Hope this helps
Cheers