Microsoft has released the tool fro creating Word Stylesheets for Microsoft Dynamics NAV 5.0. You can download it from PartnerSource here. It includes one FOB file with new objects, which are used to define the stylesheets, and documentation.
The process of creating styleheet is very easy: you create new card for the styleheet, where in header you define the base table and in lines you define all used tables, fields you want to export and relations between tables (e.g. Sales Header and Sales Lines). After that, you can create Mail Merge document, where you can create the text, formating etc. using the Mail merge fields with all the fields you defined in NAV (you can use Work Date too...). After closing the document, NAV will import it back and will try to transform it into StyleSheet. After that, you can use this stylesheet for exporting data from the base table. Easy, isn't it?
Of course, the tools can have some bugs, do not forget that it is the first version.