jedispara

I'm going to be in the situation where my primary machine is a laptop (mac). Now I have more data than will fit on it, and I want to use Bittorrent sync in tandem with a NAS. But I won't always have the laptop plugged into the external hard drive at the desk. Is there a way to have it so that bit torrent sync will only sync when the external hard drive is plugged in (AKA at home base and not on the road)? Cheers and TIA.