Looking to change opacity of a lens flare based on its position on screen to shine through text

Hey there! I am very bad with expressions, but let me try and verbalize my idea here. 

I'm looking to essentially create a template for a project where a lens flare will fade in quickly as it passes over a layer of text, fading out between letters. It would need to be something that can be dynamic in the sense that I can change the text layer to anything I want, but the lens flare will show up as it moves past the text.

An example would be: I have a sunrise matted behind text, and as the sun shines through, the lens flare appears in the foreground in front of the text, but disappears as the sun goes between the letters. The background is black to paint a bit of a picture there. 

Hoping this is something I can do instead of manually changing the opacity for every export I'll need to do.

Thank you in advance for your time and help!