You have 2 options. The easy way is to use the Eurotherm modbus OPC server. You can try it out. It will let you connect to it for 30 minutes at a time. If that is the way you want to go, then you will have to buy that option. The other way, which is free, is to use the Labview generic modbus drivers and get the command set for the 3500 from Eurotherm. They have always published this information, so I am sure it is available.