I'm used to calling these multi-value fields - what are they in FMP?
A bad idea!
What you want here would probably be a checkbox with a value list, but FileMaker is a relational database – if you want to assign multiple categories to a product, create a child table of ProductCategories, related by the primary key of Products.
It's OK to use so-called multi-value keys in UI processes or for meta-data, but you shouldn't store your business data in this manner. Imagine trying to create a report of Products by Category, and you see the first of many problems …
Thanks for the help.
Curiously, with my usual platform that report would be child's play. :-) That being said, it's a flat-file system that can fake relational.
It's the UI side of this that I'm having the trouble with. Checkboxes won't work, firstly because of the number of categories and secondly, because the categories themselves will change over time. A probable minimum of 60-70 checkboxes would be a nightmare from a layout point of view, especially when the number isn't fixed or known ahead of time.
I'm thinking that either using a Value List or a calculated lookup of the current categories to initially populate the drop-down is the way to go, storing the selections in a related table (as you suggest), but I have no idea how to actually create a multi-select drop-down in the first place.
I meant that you were probably thinking of checkboxes – not that it's a good idea to use them here.
To see how to implement a UI for selecting categories and creating child records (and having a proper structure in the first place), see this example file.
Ahh - sorry, I misunderstood you.
Thanks for the example file - I'll have a look and see what I can learn.