[Koha] exporting MARC records on mysql conditions

Hi, the online export tool for bibliographic records allows to select records in a given range of either biblio number, or item call number, or accession date. Would it be possible (perhaps via an off-line script) to select records fulfilling other constraints? (Say, a full mysql "where..." condition.) If not, would it be possible to extract (single) MARC records by off-line invoking export.pl on (single) biblio numbers? (One could have saved a list thereof in an auxiliary file, and then iteratively call export.pl via some script.) Many thanks in advance. Giuseppe.