Personally, I don't think it can be done.
A selection list field has to be tied to a list. It can't be tied to a dynamically created array, as far as I can tell. Since changes to a custom list won't be seen by users already logged in, you would instead have to create the dynamic list every time you open a test. But with multiple concurrent users accessing the system, that wouldn't work.
I say go back to the person who said it could be done and have them figure it out. Or, contact HP Professional Services and pay them to figure out how to implement this customization.
A selection list field has to be tied to a list. It can't be tied to a dynamically created array, as far as I can tell. Since changes to a custom list won't be seen by users already logged in, you would instead have to create the dynamic list every time you open a test. But with multiple concurrent users accessing the system, that wouldn't work.
I say go back to the person who said it could be done and have them figure it out. Or, contact HP Professional Services and pay them to figure out how to implement this customization.