How to make a Shrinking Header?

Hi,

I want to create a header that shrinks as it goes. So when you scroll, only a part of the header continues with the page. How can I do this with Corvid? I understand that I have to create two separate boxes in my header, one for the "#largeStrip" and one for the "#smallStrip" but I'm not sure what code to use for the scrolling.

Thanks! Hope you can help and have a great day!