How to Run SharePoint Usage on File Types

I need to see if all of our users are using Microsoft Project to see if it's worth the $38.40 per month (it's SUPER expensive).  All of our project files are stored in a single document library across many different project folders.  

Is there anyway to track which users are accessing specific files (ie mpp files) that can show how many times a user opened/read these files?  The Admin Centre Reports can show me how many files are accessed by a user for any day, but that's every file.  

OR

If this can't be done, is there any other way to monitor if a user is using an application without having to install monitoring apps?