Hi.
Unfortunately we are not very familiar with LabVIEW, so we can’t offer any help with programming in it. However, a good way to get started would be to first figure out how to send bytes to a serial port with LabVIEW by reading NI’s documentation, and then learn what bytes you want to send to the TReX by reading its user’s guide, and put the two together. This vi that was made by a community member for controlling one of our other products (the Maestro USB Servo Controller) might be helpful.
-Claire