I need to create a new field "related" which is automatically populated (comma separated) with the IDs of all the records which are related to that record.   Records are related by having the same value in one or more fields.

For instance, I need it to look for value "X" in field "A", and/or value "Y" in field "B". If "X" or "Y" are present in a record, then amend the ID of that record to the list of IDs in the "related" field.

I'd be really grateful if anyone can help