splitting fiff files

Hello
I have a raw fif data file that I would like to split into two files.
The file contains data collected originally from an EMG recording, and I'd
like to take the first N seconds and put that into file 1 and the all
remaining seconds into file 2.
Is there a tool for this, and if not what matlab commands should I be
looking at?

thanks

Daniel Goldenholz MD, PhD