VertexTexCoords

I've seen this:

VertexTexCoords surface,index,u#,v#[,w#][,coord_set]
Parameters
surface - surface handle
index - index of vertex
u# - u# coordinate of vertex
v# - v# coordinate of vertex
w# (optional) - w# coordinate of vertex
coord_set (optional) - co_oord set. Should be set to 0 or 1.

coord_set ?? does this mean we can have two UV coords per vertex? if so, how do we set this, and how to use?

"does this mean we can have two UV coords per vertex?"

-- yes

"if so, how do we set this"

-- using the command above

To apply a texture that uses the second set use the texturecoords command to specify what coordinate set the texture uses - the apply it like normal.

Note that Ultimate Unwrap now supports a second UV set so you can set them in that tool and export to b3d file format. Normally the 2nd UV set is used for lightmapping (and is therefore set automatically in your lightmapping tool) but I've been using it for tricky texturing effects on terrain.