The manufacturer of the balance is a pretty important bit of information to know here. It could well turn out that there is driver software (a software programming interface written specifically to make communicating with the balance easy) available in LabVIEW or some other programming language.
At the least, you could probably find out the list of commands that the balance supports on the manufacturer's Web site and then write your own serial I/O code in LabVIEW to interact with it.
Regards, John Lum National Instruments
> I want to connect a balance with a PC. >I search a free soft to capture the data on the rs232 port. >thank