Music Organisation / Multiple Computers

Morning,

I have a laptop and a desktop and a NAS device. My laptop is my gigging computer and up until recently it's been the only computer I've had. I've now purchased an additional desktop PC and have moved all my main functions across leaving my laptop with the basic software I need to play out such as Traktor etc.

Now, I obviously keep my laptop loaded with the music I'll be playing out and every now and again I'll backup to my NAS using GFI Free Backup - amazing piece of software for free, incidentally.

And so after purchasing a few NI items I have a couple of copies of Traktor spare and so I've installed a copy on my desktop so I can prep stuff with a view to exporting the playlists to the NAS and then import to the laptop.

What I'm wondering is, is there a piece of software which exists that will enable me to use the NAS a central repository and update specific folders on my laptop and desktop as they change? I don't want to replicate my entire MP3 collection across three devices, just the ones I specify and it needs to be done on the fly.