This is an example of an conditional value list. You can find a tutorial about it here: FileMaker Tip - Conditional Value List - YouTube
Basically you have a table that holds the values in your 2nd list. It contains a field called "Type" and a field called "Choices".
For all choices that match Type A, you fill in those records with A for the type and the choice.
You then create a relationship from your parent table to the value list table. The relationship is set to be TABLE::Type = ValueListTable::Type. Then set up the value list for Choices from this table, using the related values only.
Choosing Type A will show only those records in the ValueList Table that have type A.
Check out the video. It is very clear.
And I threw together a little sample file for this. Pretty simple, but it shows how to set up the value lists.
Thank you Jeremy and that worked perfectly by following your example. The challenge I have now (probably a simple answer) is the layout (called Contacts which is based on the Contacts table) is where I want to add these fields to but they are currently unrelated. I still find relationships a bit confusing so what relationships do I need to make it work on my Contacts layout.
Thank you very much. Extremely helpful so far.
In the contacts table, you simply create those fields that I provided in my example. Since you need them for the relationships I showed in my example, the fields have to be in that table. And you set up the relationships from contacts to the Values table using the same way I did in the example file.
Please let me know if there's more that I can help you with.
Perfect Jeremy and thank you immensely. It was the missing piece to my puzzle. Have a great day.