rsyncing in the background

Hello,

I would like to use the possibility of launching background activities in exmh 
ro run a rsync program (basically I run exmh on my "main computer" and I would 
like to use exmh also on my notebook while keeping the local mh folders 
synchronised with those on my main computer) and then flist. I never 
programmed in tcl but I assume I just would have to add a Hook_Background() 
procedure in user.tcl.

Is that correct and what should I place in this procedure to run a unix 
command such as rsync then call flist ?

Thanks for your help

Marc