Single surface help !

I have try to make this function but don't work :(

I haite single surface system :/

Function AlphaSprite(sprite,Alpha#)
s.sprite = Object.sprite(sprite)

VertexColor s\surf,s\verti[0],s\r,s\g,s\b,Alpha#
VertexColor s\surf,s\verti[1],s\r,s\g,s\b,Alpha#
VertexColor s\surf,s\verti[2],s\r,s\g,s\b,Alpha#
VertexColor s\surf,s\verti[3],s\r,s\g,s\b,Alpha#
End Function