As @Michael mentioned you can use the keyboard class to measure duration. Here is a post with a code snippet that should work in your coder view.
The focus of this post is on time locking the start of measurements but the code there is the same. One thing I would say is if you can try to implement this as code snippits in builder that would probably be simplest in the long run. But at the moment hopefully this code snippits helps in showing how you can implement the keyboard class!