back gesture dell precision 5520

I'm trying to achieve a heavily relied upon gesture on my new precision: the back swipe.  I'm accustomed to it being 3 fingers, but I'll take any gesture better than meandering the cursor across thousands of pixels to a tiny target at one edge.

I found: 

http://en.community.dell.com/support-forums/laptop/f/3518/p/19457075/20146166#20146166

But, while seeming promising, the instructions are too vague to follow in practice.  

I really hope there is some option for this.  It was really useful.