Not completely sure what you want to do, so I will answer in several ways:
To add a fraction of a second to the time stamp in the file:
In the TimeStampFormat property change it to:
dd-MMM-yy HH:mm:ss.fff
To sample data at intervals other than 1 second, change LogInterval property. For example for 0.5 second, use the value 500
Keep in mind that a PC is not a real time operating system the time samples are not going to be extremely deterministic. You may be able to get slightly more repeatable results using a separate driver instance, setting the PollRateOverride, and using a DataSubscriber pointing to that instance. Then in the DataReturned event handler, write the value to a file using code.
