you can do it in brians,
ie. lets say UserDRO 2000 is where you put your timer value you want to send out.
in brain, put your input as UDRO2000>no op>serial modbus 0
so in your serial set up, the local var 0 would have the value of UDRO 2000 and send that to your register in your PLC.
If you want to do "Floating point" values then you will need to send two seperate 16 bit registers out, to two differnt registers in your plc, then combine the at the PLC side, you can send them back the same way, by first seperating your floating point values to two seperate register back to mach.
scott