How do I configure an ordered list using dynamic select lists?

This ordered list contains multiple options that can only be selected once. This means that users will have the choice between 3 options, then two, then one. This is helpful when configuring forms containing the need for users to choose the priority of multiple items. This configuration is superior to using normal select lists in this case as user error can end up choosing one option multiple times, which is not always ideal.

Select List 1 contains 3 values, A1, B1 and C1. I have put the number 1 after these 3 options as it is the first select list, and so that the item's option keys can be unique.

Next, I created Select List 2, which is a Dynamic Select List. This feeds off of the selected option on Select List 1:

There are 6 values in this select list; B2A and C2A for A1, A2A and C2A for B1, and B2B and C2B for C1. I have put the letters A and B after each value to prevent the names and keys from being identical.

So, if a user selected A1, they would have the choice of B2A and C2A.

After this, I created Select List 3. Here is where the final value is selected:

There are 6 values in this Dynamic Select List. The Value C3A will appear if A1 and B2A is selected on the previous select lists. This is because the parent answer of B2A was selected on the second select list, and that can only be selected if A1 is selected on the first Select List.

On each of these final select lists, no matter the order of values chosen, there is only 1 value remaining to be chosen. 

The letter suffix on the end of the value’s names are to denote their appearance in the select list. For example, on the screenshot above, the option “B3” can be selected twice (as A and C both need B as a final option) and have thus been designated B3A and B3B)

With this configuration, at no point will any user be able to select one of the same letter. It will always be ACB, ABC, BCA, BAC but never BBB or AAB.