Hi,
The bad news is no you cannot upgrade your GPU on the laptop. As there wont be a port or space to fit the gpu( also dont know if you can just buy laptop gpu's straight from supplier).
The only solutions would be either upgrade to a new laptop or source/build a external GPU set up. Dell have started making external GPU set ups for their alien ware 13 model, so have a look at their site just to see what they have done. Also found this site that is an example of a self build external GPU
http://www.neowin.net/forum/topic/1191969-external-gpu-for-laptops-supercharge-your-graphics/
Hope this has helped and please correct me if i got anything wrong