A very open ended question... but is there a way to do this?

I'd like to take over the application of a style (Heading 1, as an example) and do some custom processing before (or after).

I can, of course, create my own button... however, ideally, I'd like to be able to use the built-in QuickStyle gallery or Styles Pane to apply the style, and still do custom processing.

I had thought of using a similar concept to Greg Maxey's monitor concept... but that seems like a lot of overhead, although that would be slightly more desireable than entirely recreating a custom QuickStyles Gallery and a custom StylesPane.

Broad thoughts/brainstorms welcome... unless I'm missing some old hidden feature (a la Sub FilePrintDefault type thing).

EDIT: Word 2010 is my primary concern, although any ideas on any version are more than welcome