Black Sprites

This is not so much a request as it is a question, but i have no idea where else i would put it.
Im currently trying to make a Black sprite for a weapon skin i made, but so far how the game is set up, If a sprite has black anywhere, those black areas are completely invisible. tryed Inverting colors, ended up with a giant blinding white Box, and an invisible hole where the actual sprite is supposed to be. is there any way to Reverse it so that White is invisible, and black is opaque, most probably in the VMT?
thanks