In the importer you can set it to do so though the alpha channel in your tga file. Using your image editing software, go under channels and create a grayscale channel that is colored a gray or white (white is shinniest) for areas you want it to shine and black for areas you don't want it to shine. Name the channel "Alpha 1". Back on the importer, in edit vmt, after clicking the tab "cube map" and selecting anything but "none" (I like world cube map) you can then click the tab below it and select "base alpha" to make the alpha channel define what is reflective. I forget how to make parts transparent but it's probably though the alpha channel.

Try here. You might or might not beable to figure it out from this, I found it hard.

I already got this right, but thanks anyway.

The only thing I cant do now is making the texture semi-translucent, shiny and paintable at the same time. If I make it not paintable, I can make it semi-translucent and shiny at the same time, but if I set it for paint, I can only make it shiny.

Ah I have the same problem since its all done though the alpha channel and there dosen't seam to be anyway to make the cube map, paintablity, translucientcy, phong mask, and maybe some other things though anything but the alpha channel. If you find out how please tell me!