Item Rule for validating dupplicated Cross-References

Summary:

Content (required):

Hello! Customer is requesting a way to avoid users assign twice the same Cross-References. As far as we could research there is no standard functionality that let us achive this, so we started thinking about an Item Validation Rule. The issue is that we couldn't think of a rule that could work (like a count of the same cross-reference types)

Version (include the version you are using, if applicable):

22D

Code Snippet (add any code snippets that support your topic, if applicable):