TOC numbering

Hi, I'm working on a design of Table of Contents feature and I need a help of some XWiki expert ;-) As an optional feature the {toc} tag should allow to specify if both TOC and the actual headings should be automatically numbered (the same how it works in Word). To add the numbering into items in TOC section during a processing of a TOC velocity macro is simple but to add the number just before a text of heading in the actual content means to change the existing content in the middle of rendering. I was thinking of modifying filter.heading.print Radeox filter (BTW an easy way for adding an anchor into headings) to encapsulate the heading text by a velocity macro (which will then share the same numbering logic/variables with the TOC macro) and then let it process by VelocityRenderer. Unfortunately it doesn't work because VelocityRenderer is called before RadeoxRenderer in the chain of renderers. So, is it possible to change content of document being rendered from within a velocity or groovy macro? If not, is there other flexible way of this kind of changing of existing document content during rendering phase than to modify an existing renderer or create a new one? Thx, Jiri.