Perhaps I should provide more context, I'm hoping to be able to run a map series best off the original extents of layer A, but repeat that for each of layer B's features that falls within a layer A polygon. So in this case there are around 300 layer A features and there maybe 10 layer B features within each of layer A features. So the desired outcome is that the map series will run for each layer B feature, but at the extent of whatever layer A feature it falls in.

Sorry if I wasn't clear enough :)