Hi Wilhelm 273
We can use an image mask for this. (Also the preserve opacity function as advised by Fox)
We want to create an image mask source from the pink box. You could make a clone of the box for the mask source, or you can duplicate the box and link all the functional parameters to the original to ensure it animates exactly the same. (Personally, I prefer to use a linked duplicate rather than a clone.)
Apply the image mask to the logo
Assign the mask source to the image mask. It will be set to 'add' by default which is what you want.
If you can provide a link to the project file in the youtube description, then I can prepare a working example for you.
Using an image mask is the answer to your immediate question. However, for this kind of animation, you might want to consider the 'functional integrity' of your method. If you want the pink box to be adjustable - for width/length, and for height - then you have to consider the 'starting position' of the logo. For example, if you want to increase the pink box height, then you will discover that the logo will be visible within the masked area too soon. If this becomes a problem, let us know and we can review solutions for this also.