Nikon - Filming HD in the dark, lighting

I'm going to be filming in a dark dance club using my nikon d300s, and I have a Nikone SB-900 speed light. Is there any way I can switch my speed light to "always on" in order to light the dark club in order to film?

If not, what equipment would you suggest?

When you say "filming" do you mean you are shooting video?

A flash unit is designed for shooting still images, so no, you can't just turn it on and shoot video with it.

What you will need is something like this.

http://vidled.com/

Or this

http://www.studio1productions.com/LED650.htm

Filming? That will be expensive - especially with 35mm film. The film stock along will be many
hundreds and then there's the camera to shoot it with - what a project. Or is that you just don't know your terms and have done zero homework to learn them?

You'll need lots of light - a kit would be best. Personally I prefer Lowell - and excellent brand.
These kits aren't cheap but they certainly will do the trick whether your "filming" or shooting video.
In either case a Lowell kit - perhaps $600 or so, will do what you want.

Here's a great place to shop for lit kits. Http://www.bhphotovideo.com/