2 of 2 people found this helpful
What you are describing is called a "conditional value list" (CVL) where the value in one field controls what values appear in the value list of another field. There are actually quite a number of different ways to do that in FileMaker. The most common method that you'll find under the "Conditional Value List" label uses a relationship to control which values appear in the value list. Other methods give you a filtered list to pick from, but don't use a value list at all to produce that list.
Here are some instructional files on the topic. Each file has multiple working examples and each example has detailed documentation on how to set them up and how they work. Plus, you can ask questions about them here in the forum if you need to.
And please read the "Geek Busking" info on the first Intro layout...
Thanks Philmodjunk! I'll go through those tomorrow and hopefully get my head around it :-)