Is it possible with e720?
I am going to say no on a 99% sure assumption. The only laptops that I know of which can have graphics cards upgraded are the SUPER expensive ones that allow SLI and Crossfire. Those are ridiculously expensive.
Laptops are designed to be small and portable. They cram as many parts as they can on a single board including the video. Sometimes it is a separate card that holds the GPU, but this is still proprietary.
Upgrade laptop graphics = New Laptop.