Good idea CK. Here's quick how to.
Grab the AutoHotKey application, install or whatever
http://www.autohotkey.com/download/
You will need to launch AHK and then right click on it's taskbar icon and choose
'Edit this script'
There'll be a lot of text in there. All you need is the following text in there.
Mbutton::
Send {F9}
Sleep, 3000
Send {F9}
Anything with a ; in front of it is treated as a comment and ignored
What this does is listen for the Middle Mouse button and then performs the following actions, Sends a keystroke F9, waits 3 seconds and sends another F9. Simples.
Now for MSI Afterburner
To record video and sound you'll need the Beta.
http://event.msi.com/vga/afterburner/images/MSIAfterburnerSetup220Beta.zip
Install and run the program.
Go to Settings.
There's a Video Capture tab, go to that.
In the videos I've made so far I had the Quality at 80% and the frame size at 1/2 frame and noticed no lag or delay so have changed it to the settings shown but as of yet have not tested. I found the videos a little low def recorded at only 840x525 and you couldn't quite make out the name of the victim so hopefully the full frame recording won't be too demanding or too much larger in file size.
30FPS is just fine I think.
Then when you run both AHK and MSIAB while playing BC2 you'll get a recording for every time you press Middle button. You'll get a recording for every stab but also every fail stab and door breaking stab too.
You may also need to edit MSIAB to not crash your system with Punkbuster and it's retarded detection systems. To do this you'll need to rename the RTCore.cfg to something like RTCore.cfg1, you'll find this file in the MSI Afterburner root folder.
To create a montage I just remove all unwanted videos I've recorded and chuck them all in sequence and encode with Windows Movie Maker.