Question about Showtool detail slider and texture swapping from

I am using a 10x10 grid of single poly planes to make a cornfield. The cornfield needs to be very visible from air, but since most of the surface area of the polygons are tranparent, they get lost at a distance and the cornfield ends up looking like a gray blur (mipmapping). I went ahead and made 4 textures, one for each detail level progressively getting greener so they would show up better at a distance.

I have my model set up with meshes for 4 detail levels(blah2, blah50, blah100 and blah200) each of which has a different texture.

Now when I use the detail level slider in showtool, it will show my various levels with their textures correctly.

How do I get it to do this in-game? If it works in showtool then there must be a way. What value is the slider changing?

Any help with this would be greatly appreciated :)