As I understand your problem is to observe the file for changes and than refresh the data in your app. I see to possible solutions with the simplest that you install a timer which check the last modified time of the file and than reacts.
But more elegant is to observe the file or directory for changes. In the Microsoft article
Obtaining Directory Change Notifications
is not only described but also some sample code how it can be implemented. I also would check the last modified time to avoid excess execution of the update.
It is very important to cleanup all handles at exit!!!