Hi TheSimo
There's a handy product on the market which splits a 4-20mA signal in to 2 or 3 separate channels - called a loop splitter. It means you can do what you want to one channel, the other won't be affected.
Take a look here for example ...
Hi Markems
If you want a simple, user-friendly converter to take a loadcell and convert it to RS232 or RS485, London Electronics do a nice model, the INT-L
It will power up to 4 loadcells and lets you scale them to engineering units.
You can add output options to it, such as RS232, RS485...