Installing outdoor flood light off of crawl space light switch

[thelavender]

We have a crawl space that is situated right above the back porch where I want to install an outdoor flood light. The crawl space has a light switch in it for the crawl space light. Is it possible to wire the flood light off of this switch in such a way that the light switch will not effect the flood light? Do I need to run romex from another junction box to where I am going to install the flood light?

EDIT
Looking around a bit I did think about a combo switch outlet to replace the switch in the crawl space. Could I use that and then wire the flood light to the outlet that would constantly have power fed to it? Kind of like in this video?