How to stop vertical zoom?

I am now comfortable using the mouse wheel to move back and forth on the time line, and to zoom in and out, using the mouse wheel, combined with various keys.
However, is there a way to prevent tracks from vertical zooming?
 
I never want this. When I have pressed F, to fit tracks, I still want to zoom in and out horizontally, but never vertically. As it is now, when zooming in horizontally, using the mouse wheel, the tracks also start to "unfit" vertically, arrrgh..
Ingvar

Thanks!!!!!!!!  
Finally Sonar behaves..
 
Ingvar