Hey Todd, The Write LabVIEW measurement file express VI is built on top of other LabVIEW VIs for writing to file. If you open the help for the Express VI it lists the VIs and functions the Express VI utilizes. If the data you want to write does not work with the Express VI you can always use these VIs directly. LabVIEW ships with lots of examples for writing to file that may be helpful to look at. You can find these by going to Help >> Find Examples.
I hope this helps! Sarah Miracle National Instruments
