Warning on duplicates

Dear All,

I am trying one use case in Anaplan and it is as mentioned below:

User will input an item in the list formatted line item. If the item is repeating itself then it should highlighted using conditional formatting. It is dimensioned with dummy flat list. Below is the screenshot. 

List Item1, List Item2 etc. is a list and Property 1, Property 2 are list formatted line item.

Thanks already for your support.