It sounds like you have added the field from your category table to your current layout. (What table is this layout based on?) Thus, selecting a value in this field modifies the first related record in your category table. Chances are this change to that record results in a condition where your layout's current record is no longer related to that category record so it disappears when you commit the record by clicking on the layout background.
Replace your category field with a field defined in the layout's table and update your conditional value list's relationship to work with this new field and you should be able to resolve your problems here.
Wo you guys are fast :-) There are three tables
1) a distinct Category table with only about 15 records.
2) a Sub-Category table with about 40 records (Category, Sub Category, Item number)
3) an Inventory table with hundreds of records. (Sub Category, Item nuber and lots of other fields about the item)
The active table is currently Table: SubCategory...
I am very new to Filemaker (on day 6)... So, Which of the three tables should be the active table?
... the combination of ( Display Data From) and (Values From) is a bit confusing...
also... most important! Both the first two tables must be Read Only.
I do not want the user to be able to modify Category or Sub Category... so when the system itself is changing data it kind of freaks me out.
That was it...... I changed the category list to be selected from the Sub Category table and now it seems to work !!
Thanks very much.... but do I need the Distinct Category table at all now?
It would make things more simple to get rid of it.
No simple answer to your question. You'll need to look at what data you are putting into each table and how you use the table now and how you might use it in the future. If all the data in the category table is repeated in the sub category table, then the category table may not be needed as a separate table.
If you haven't already seen these, here are some links on conditional value lists that you may find helpful:
Forum Tutorial: Custom Value List?
Knowledgebase article: http://help.filemaker.com/app/answers/detail/a_id/5833/kw/conditional%20value%20list