I'm trying to make a program that will constantly check the size of a file and if the size of the file changes, make the program do something. The file is an html file so another method could be to constantly check the source of it and if the number of characters changes, do something. 

I think I could do that without much trouble but the thing I'm having a problem with is having something constantly check the file. Is there a function that can do that? I'd like it to check every 10 seconds.

edit: The operating system is Windows 7 64-bit