Just click on the box where space is assigned as default and then scroll your mouse wheel up or down to set the bind.

Mouse-wheel scrolling doesn't work the way it should in all programs. Here's a quick fix to make it work consistently, everywhere.

This feature is intended for folks who don’t have a scroll wheel, but it works just as well with scroll wheels–and I know many people who prefer the speed of middle-click scrolling to the slow ...

Logitech has introduced its Revolution mice, which use the "MicroGear" scroll wheel that can adjust between free-spinning and ratcheted click-to-click modes.