I wouldn't use two sets of uv co-ords for that. Because, when you load a texture in, you can move the texture anyways. So just do:
Make sure that you use the two clamp flags, so the texture doesn't get tiled. No need to use 2 sets of UV Co-ords :)
<createvertexs/triangles> tex=loadtexture("firsttex.bmp") tex2=loadtexture("shadow.bmp") EntityTexture model,tex,0,0 EntityTexture model,tex2,0,1 MoveTexture tex2,0.5,0.2 ;<<<<line for moving texture.
Make sure that you use the two clamp flags, so the texture doesn't get tiled. No need to use 2 sets of UV Co-ords :)