Snow Leopard and File Sharing

[mgirg]

I have a new Macbook which I sync with my computer at home with Chronosync. To do this I have to have the file sharing system preferences turned on on the Macbook, but I dont want it on all the time for security reasons (ie when I am out and about connecting to other networks)

So is it possible via an applescript or automator or something like that to set up my macbook so it will turn on file sharing automatically when connecting to certain networks, and off automatically when not connected to those networks, or am I stuck doing it manually?

Thanks

Mike