Glossy Window Pane Effect

This is my first time asking a question (or uploading a .story file), so they keyword is compassion :)...

I'm trying to understand how to achieve what I've always called the "window pane effect." It's the effect of diagonal lines running across an animated window that makes it look a little glossy and more realistic. Not sure how to do this.

I've attached a .story file of a window that I created. Please have a look. I'm using diagonal parallelograms to try to get this effect, but I'm not crazy about the result. How would you make it better? 

Thanks in advance,

Eric