Help with Red Orchestra 2: Heroes of Stallingrad

First, like myself, there are others having problems getting past the grenade training. Says to push your MMB(middle mouse button) to throw underhand, but doesn’t work, at least for me.
Beyond downloading the Steam server Control panel, or whatever it is called. Anybody get MP working, and if so.. how ???? LAN or Internet, doesn’t matter.
Hopefully somebody has this figured out, I prefer that era of FPS battles.
Slug
Answer #1
I looked and tried editing the input.ini files to get the middle mouse button to work, still no go.
I have a Logitech mouse, ordered a Razor to replace it. Hopefully someone sees this with some answers