Graphic Card & Display connected to another card

Is it possible to have a graphics card (preferably ATi) send the picture to a monitor that is connected to another card (that one is already ATi)? The idea is that I'd like to use an external graphics card with my notebook (installed in ViDock 2 and connected through ExpressCard) but still use the integrated notebook monitor with it instead of a separate monitor.

As far as I understand it, this Matrox thing does pretty much the same thing as the ViDock 2, except it doesn't give you the choice of what graphics card to put in it and it doesn't even seem to have a graphics card in it at all (well, not one that would improve performance, compared to my integrated Radeon HD 3200, anyway). All it does is let you connect more monitors... and what I want to do is the opposite of that - I want to use my integrated monitor with the external graphics card.