You can do this in scripting either automatically every x amont of time or manually when someone presses a button. The script will be something like this:
fileStr = system.file.readFileAsString("C:\\Path\\To\\File.txt")
Of course that script is really simple, so in order to give you a better script what does your file look like? Is it a CSV? There are several ways to read in values and write them to tags.