I tried putting in delimited data via a checkbox set entry field (when you create a new entry in special_items_list, you can check several types of surgery and it forms a delimited list in the field), but this did not work.
That approach should work. I suggest taking a new look at it to see why that it didn't.
This Demo File just so happens to illustrate the check box method: https://www.dropbox.com/s/j6qf0z9fnem3uxd/ConditionalValueListDemo.fp7
It actually demonstrates how check boxes can be used with the match field on either side of such a relationship.
You are right, Phil - it did work! When you said it should, I went back and looked at what I was doing. I will tell you why I was thinking it didn't work (to maybe help another newby). To check to see if the relationship worked, I had added the related field to a table view from my appointments, thinking it would show me the results - which it did, but it only showed the first record to match. So I assumed it wouldn't work for the multiple match.
But after reading your post, I went back and constructed the value list based upon that relationship (where I had checked multiple boxes for several items), and indeed it did work. So I am good to go.
In my special_items_list record, I now have a checkbox set for the special_items.appt_type field that has cataract, retina, plastic, etc., and if you check more than one, the field ends up with a delimited set of all the items checked - and the value list matches only the records that have the matching appt_type. So if the appointment.appt_type is cataract, it shows only cataract items, but if it is retina, it shows only the retina items - so an item that has both retina and cataract checked (and thus both values in the delimited set) shows up in both lists.
Thanks again, you are a font of FileMaker knowledge!!