Unless your laptop has a very fast external interface like Thunderbolt or USB 3.0 or preferably 3.1 you're going to have a huge bottleneck in terms of the interface between the external GPU dock and the laptop. You have a low end Sandy Bridge based laptop judging by the processor and you might be lucky if it even has USB 3.0, it definitely won't have Thunderbolt or USB 3.1.
Even if you didn't have an interface bottleneck, a mobile CPU from 5 years ago is going to be a bottleneck in a lot of games simply due to the low clockspeeds those chips ran at to keep within the lower thermal and power consumption specs for a laptop.
Bottom line, it isn't worth doing, even if you just had the 960 lying around, you'd still have to spend around...