Graphics on laptops is different to graphics on a desktop.
Along side the USB, ethernet, firewire etc ports that are external ports seen on both laptops and hard drives, desktops have internal expansion ports, such as PCIe, PCI and internal USB slots. Laptops have nothing like this, what you buy is what you always have. You can upgrade your hard drive, you can upgrade memory, to a certain extent you can potentially upgrade your CPU, graphics however, 99.999% of the time (in your case as well) the graphics are integrated, meaning they are a chip on the motherboard, they are soldered on there and they can not be removed and replaced.
In short, no, you can not upgrade the graphics on your laptop I'm afraid, your only way to get better gaming performance is to get yourself a new system. If gaming is your thing, a desktop is the way to go. If you don't have the room for that, or if you require the portability of laptops, unless you are able to fork out a small fortune for not all that great gaming performance, whilst losing out massively on battery time, you won't be able to