Hi Anward,
When you create a file, you could index the name by time or something unique (iteration number for instance).
So if the vi that creates the file has a loop which keeps tract of the test cycle, then you can place the filename creation within this loop. If it is located within a sub-vi which is called at every cycle, then create the name there. Make sure you close the written file at the end of each cycle.
Use the "Open/Create/Replace File.vi" located in "File I/O" of the Functions Palette. Wire the option to Create new file.
JLV
