hi matt, im not a modeller, but if i remember rightly, the only way you can do it is by using the cut face tool. This adds a edge, which in turn crosses another edge thus creating a vertex. I dont think you can just add vertex's. Maybe im wrong.
Or using the edge loop tool, or split polygon tool all in the modelling menu, edit polygons.
Maybe some modelling genius will be able to shed some more light on this. Like i sed, im not into modelling but ive dabbled in it and this seems one way out.
those who succeed are only the failures that never gave up.