captivate 8 image masking?

Hello!  I have not found a real answer to this question in the forums or anywhere else online, and am hoping someone can let me know if this is possible to do in Captivate (version 8 in my case)

I need to mask an image with a shape, so only the area inside the shape would be visible (just like it would work in Flash/Animate).  The image needs to be animated, so I cannot just crop it to fit whatever area it sits in, unfortunately.

Highlight Box object has a functionality similar to the one I'm looking for, but because it simply fills the outside area with a flat color rather than properly masking a layer underneath, I cannot use it.

Is what I'm looking for an existing feature in Captivate?  If not, does anyone know of any useful workarounds that can be done inside Captivate, or is going with JavaScript the only viable way to achieve proper masking?

Thank you very much!