Comparing text file before proceeding

Hi,

        I have a line of numbers in a text file (from a real time simulation that is updating at approx 1 Hz. I need to in a while loop open the file make sure the the numbers are diiferent(I'm not reading the same file twice) and if the text file is new (different from the previous text file proceed with the rest of the code I wrote. Can I use a feedback node?  Thanks