Can I add a new graphics card in the Express slot

I don't know much about my HP laptop's graphics card except that it doesn't have the technology to play some of my son's games - vertex and pixel shading?? It has a PCMCIA express slot, and I'm wondering if it's possible to buy a graphics card which installs into the slot and run the graphics through that card instead of the one integrated onto the motherboard? If so, what do you call these cards and what type/where to buy?

Thanks for any help. Terry.