I'm trying to use the checkboxes to filter the lookup. The checkboxes are for Material Categories.
When you check a box, I'd like the multi-select options to only show for the category or categories that were selected in the checkbox column.
In the Materials list, only one category is selected per list item, so there wasn't a need for a checkbox on this end.
In the Events list, they should have the option to filter on more than one material category to get desired results from the EventMaterials multi-select lookup.
Does this make better sense?