Blitzmax GL Fog

I've been reading some online OpenGL tutorials on how to create fog, but I can't get it working in BlitzMax. Does anyone have any samples on how to create fog/clouds using OpenGL in Blitzmax? I'm making a 2D sim and I would like to add fog and/or cloud cover to obscure portions of my tile map.

I'd be very interested to use opengl fog too! Maybe I could put some really cool nebulae in the backround in my space shooter with this?

http://www.blitzmax.com/Community/posts.php?topic=45455

The demo code there uses fog.

If it's only 2d, all you need is SetBlend LIGHTBLEND