HELP! biblatex, mixing interfaces, xref: come fare?

Salve

sono molto grato a chi mi aiuta a capire come realizzare le seguenti indicazioni, tratte dal manuale di biblatex, sezione 4.11.1:

++++++++++++++++++++++++++
Another case in which mixing interfaces is helpful are styles using cross-references
within the bibliography. For example, when printing an @incollection entry, the
data inherited from the @collection parent entry would be replaced by a short
pointer to the respective parent entry:

[1] Audrey Author: Title of article. In: [2], pp. 134–165.
[2] Edward Editor, ed.: Title of collection. Publisher: Location, 1995.

One way to implement such cross-references within the bibliography is to think of
them as citations which use the value of the xref or crossref field as the entry
key. Here is an example:

` \ProvidesFile{example.bbx}[2007/06/09 v1.0 biblatex bibliography style]
\DeclareCiteCommand{\bbx@xref}
{}
{…}% code for cross-references
{}
{}
\DeclareBibliographyDriver{incollection}{%
…
\iffieldundef{xref}
{…}% code if no cross-reference
{\bbx@xref{\thefield{xref}}}%
…
}`

When defining \bbx@xref, the precode , postcode , and sepcode arguments of
\DeclareCiteCommand are left empty in the above example because they will not
be used anyway. The cross-reference is printed by the loopcode of \bbx@xref. For
further details on the xref field, refer to § 2.2.3 and to the hints in § 2.4.1. Also
see the \iffieldxref, \iflistxref, and \ifnamexref tests in § 4.6.2. The above
could also be implemented using the \entrydata command from § 4.4.1:

` \ProvidesFile{example.bbx}[2007/06/09 v1.0 biblatex bibliography style]
\DeclareBibliographyDriver{incollection}{%
…
\iffieldundef{xref}
{…}% code if no cross-reference
{\entrydata{\thefield{xref}}{%
% code for cross-references
…
}}%
…
}`
***************************

Le mie conoscenze di TeX sono minime, e non ho idea di come fare.

Grazie assai
mario

ps non voglio ottenere l’effetto voluto inserendo un comando \cite nel record bibliografico