I posted this in some other thread about version control...
But the P4Com dll can be downloaded (without viruses!) from online, i believe it's an open source dll that just makes calls straight to p4.exe
You have to download the dll and drop it into your skyrim directory.
I got this working on my machine, but there where certain issues i had
1) Bethesda uses a really weird p4 layout. And unless your p4 depot is organized identically to what they had, the creation kit p4 integration won''t work for you. I wish they put the p4 depot as a string in a config file, but unfortunately it looks like they hardcoded it. (actually, there may be an ini setting that can change this, but there's no way to tell without looking at the source

)
2) You can't seem to activate perforce integration without also activating that stupid ESM merging feature. Maybe that's what you want, but i just wanted the creation kit to check out my script and compiled script when i started editing it.
So because of those reasons I gave up investigating the creation kit perforce integration. I hope the notes from my investigation help you though.
Now when editing a script, i just right-click and select 'open in external editor' which opens the script in Notepad++
Notepad++ has a plugin called 'nifty perforce' that will auto check-out your files when you start editing them. One caveat: make sure your p4 login username is the same as your windows user name