you can communicat to all the MFC's on the flowbus useing the RS232. you have to construct the commands in Hex values and send them over the RS232/VISA COM-port.
you can get the commands format from Bronkhorst Instruction manual.
I have no idea if I am allawed to publish this commands hier. so please connatct Bronkhorst and ask them about the (RS232 interface with Flow-Bus protocol for Digital Mass Flow/Pressure instruments) manual.
in this manual you can found how the command should be send and how you can initialize the flowbus.
Note: with out initializing the flowbus, you will not able to communicat to more than one MFC's.
if you get this manual and you have a problem, just post your Problem and I will try to help.
I know that, it is a littel bit tricky to use thier commands, but it is possible and it works.