Creating a relationship (unique reference -Site column)between two lists in Moss 2007

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MOSS2007

SharePoint

*It’s possible to create a Ref(through lookup) but not possible to see it on list item B in list Y (it’s a unidirectional link)
*A work around consists of manually creating the same Ref in the opposite direction, i.e. from list item B in list Y to list item A in list X
*This is obviously will doing twice the same action, with high risks of errors .
*The final objective is to be able to perform a coverage analysis on the List Y(which one are covered or not by List X)
Example:
I create a link from list (X) A1 to list (Y) B1 and B2
Then if I go on list (Y) B1 or B2 I want to see this Ref, in an automatic column or whatever else, without having to do any more action.
All ideas and suggestions for solutioning are welcomed:)