How to make text object restricted to certain height? See the image and you understand my problem.

I have followed this excellent tutorial:
Is it possible to drive the contents of an existing text object with a text file?

I have also made my text object to be in text box with a setting of Width: 7.8 but how can I "cut" or "restrict" this dynamic text so it does not flow over the 3d phone objects screen?

Pekka Varis
Create an object above text and set it's material to holdout: