The two pieces you need to build this is first a way of telling when a new week has started. The built in function "Seconds to Date/Time" returns a number of values based on the timestamp input. Among those values are "day of the week". You can use this value to identify the time rolling over from day 7 of one week to day 1 of the next week. All you need to look for is the situation where the last time it was queried the day of the week was 7 and this time the day of the week is 1.
Second, you need to generate a new file name automatically whenever that shift is detected. Assuming the file name is being carried in a shift register, if the week has not changed, use the file name from the shift register. If the week has changed, generate a new file name and use it to update the shift register and save the data. There are numerous examples shipping with LV that show the automatic generation of unique file names.
The reason this works so well is due to the way the file IO VIs work. If you tell it to append data to a file that doesn't exist, it creates the file and then writes the data to it.
Mike...