How to create lightable box?

To create a cube like the native version you need 24 vertices. Notice that using updatenormals on a normal cube screws it up as the command averages the normals of the vertices which share the same space.
EDIT ... as per Big10p!

Anyway, this is a bottomless box lit as you want ..

Graphics3D 640,480,16,0

Pivot = CreatePivot() 
Camera = CreateCamera( Pivot )
PositionEntity camera, 0, 10,-10
AmbientLight 120,120,120
light1=CreateLight()
LightColor light1,40,100,255
TurnEntity light1,45,-205,0	
light2=CreateLight()
LightColor light2,255,230,180
TurnEntity light2,45,35,0

pivot=CreatePivot()
camera=CreateCamera(pivot)
PositionEntity camera,0,5,-10
PointEntity camera,pivot

Cube = CreateBottomlessCube()

While Not KeyDown(1)

	If KeyDown(205)
		TurnEntity pivot,0,1.0,0
	ElseIf KeyDown(203)
		TurnEntity pivot,0,-1.0,0
	EndIf
	If KeyDown(200)
		TurnEntity pivot,1.0,0,0
	ElseIf KeyDown(208)
		TurnEntity pivot,-1.0,0,0
	EndIf
	
	RenderWorld()
	Flip
	
Wend

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Function CreateBottomLessCube()

	temp = CreateCube()
	ts = GetSurface( temp, 1 )
	
	mesh = CreateMesh() 
	s = CreateSurface( mesh ) 
			
	For v = 0 To 19
		Nv = AddVertex( s , VertexX( ts, v ) , VertexY( ts, v ) , VertexZ( ts, v ) )
		VertexNormal s , Nv , VertexNX( ts, v ) , VertexNY( ts, v ) , VertexNZ( ts, v )
	Next
		
	For t = 0 To 9
		v0 = TriangleVertex( ts , t , 0)
		v1 = TriangleVertex( ts , t , 1)
		v2 = TriangleVertex( ts, t , 2 )
		AddTriangle s, v0, v1, v2
	Next

	FreeEntity temp
	Return Mesh
	
End Function

Should help.