Custom Skyboxes

I am working on a mod, but there are no skyboxes that I can use that have what I want. So I make my own, making the files starfieldBK, starfieldDN, starfiealdFT, starfieldLF, starfieldRT, and starfieldUP, and converted them into VTF files via VTFEdit. I went to the mod folder, put it in materialsrc, and when I put ‘starfield’ into Map Properties Skybox Name, ran it, put it in GMod to test, and the skybox didn’t show! it just made a vision blur for whatever passed in front of it. I went back to the mod folder, and made a folder called materials, hoping that would work. Put, lo and behold, it didn’t, after compiling and placing the map in GMod again. Anyone got any ideas? Here’s what one of the VMF files looked like:

    "$hdrcompressedTexture" "skybox/starfieldBK"    
    "$nofog" "1"
    "$ignorez" "1"
    "$basetexture" "skybox/starfieldBK"

the starfieldBK changed to starfieldDN, starfiealdFT, starfieldLF, starfieldRT, and starfieldUP with the other files. Please help! Anything will be appreciated!

Are the VTF and VMF files in the materials/skybox folder of the mod you are mapping for?

For example if you are mapping for CS:S then the files would all go in cstrike/materials/skybox.