How to apply transition to ONLY masked view

I am trying to apply the Bright Squares transition to a "content box" which has a scrolling mechanism using a mask.

So the content box is varying heights, based on how much content there is to be scrolled. But the VIEWING area (visible area) is always 500 pixels high.

However, the effect I'm using is a "center, middle" effect, and that center middle is changing based on the TOTAL height of the box, and I want the effect to only be applied to the VISIBLE part.

Is there any way to make the transition apply to ONLY the visible part (the part contained within the mask)?

Thanks,
Glendon Guttenfelder

No, unfortunately you cannot do that, the effect will apply on the whole target.