Is there a way to search for a "sibling" node in a list viewpoint

I want a validation that searches the other nodes within a viewpoint table/list . I do this when the viewpoint is a hierarchy by using siblings and ancestors. How can I call out or search the other records in a list viewpoint.

Example: If you find another record/node in the viewpoint where the node property A of that property matches the node property of the node you are adding…do this