The second tact you mention is the better one. Sadly, there is no function to query a repeater to say, “does this column contain this value?” (Come on, Axure folks!)
Instead, you must jump through a couple of hoops using the listener method. (If you Google “axure repeater listener” you will receive many examples. You will need to do this to understand what’s going on.) Feel free to ask questions if you don’t understand this listener method. It’s unfortunate that this hack is necessary,
Here you simply want to avoid adding a value if it exists. So here’s a way to check if it exists, and then add the item if not.
File: add_unique_to_repater.rp (56.2 KB)