These are called conditional value lists.
Here are some links about conditional value lists (including a demo file) that you can check out:
Forum Tutorial: Custom Value List?
Knowledgebase article: http://help.filemaker.com/app/answers/detail/a_id/5833/kw/conditional%20value%20list
Hierarchical Conditional Value lists: Conditional Value List Question
Feel free to post follow up questions here if those links aren't enough to get your value lists working correctly.
Ok, I undertsand. I don't think I am going to use a true "conditional" list because I don't want certain items to display based on what is selected in another field. Let me explain in more detail what I'm trying to do: I have a HR table that contains employee names, their title, position, etc. On a different layout (different department) I have a dropdown list where I want to display ONLY employee names that are Dentists and Dental Assistants. I don't want the list to contain Receptionists, Physicicians, Marketers, etc. This will never change. Am I still looking at conditional Value Lists, or is there some other methiod to only display the above 2 positions?
Yes, you are still looking at using a conditional value list.
Take a look at "option 1" in the Forum Tutorial link to see a method that does not require defining a relationship to do this. But do look at relationship based methods also. "Option 1", which uses a calcualtion field, is very easy to implment, but is also much less flexible than the more typical realtionship based approaches.