bug in my code and i don't see why... (short code)

Graphics3D(800,600,32,2)

SeedRnd(MilliSecs())

Origine = CreateCube()
ScaleMesh(Origine,0.01/2,0.01/2,0.01/2)
EntityColor(Origine,255,000,255)
PositionEntity(Origine,0,0,0,True)

Global Camera = CreateCamera()
CameraRange(Camera,0.1,100)
CameraClsColor(Camera,000,000,000)

Global BuildingsCount%
Dim BuildingRoot(100)
Dim BuildingXZRadius#(100)
Dim BuildingPickable(100)
Dim BuildingRenderer(100)
BuildBuildings()

Global OLight = CreateLight(2)
LightRange(OLight,3.0)
LightColor(OLight,Rand(025,255),Rand(025,255),Rand(025,255))
PositionEntity(OLight,1.5,0.5,1.5,True)
;HideEntity(OLight)

AmbientLight(060,060,060) ;DayAmbient
;AmbientLight(030,030,030) ;NightAmbient

Global LoopTimer = CreateTimer(20)
Global MainLoopMsTime%

Main()

ClearWorld()

End()

Function Main()

 While( KeyDown(1)<>1 )

  MainLoopMsStart% = MilliSecs()

  ;some code was here...

  If( KeyDown(2)=1 )
   Wireframe(True)
  Else
   Wireframe(False)
  EndIf

  SetBuffer(BackBuffer())
  RenderWorld()

  SetFont(Arial14Font)
  Color(255,000,255)
  Text(0,0,"Tris = "+TrisRendered())
  
  WaitTimer(LoopTimer)
  VWait()
  Flip()

  MainLoopMsTime% = MilliSecs() - MainLoopMsStart

 Wend

End Function

Function BuildBuildings()

 ;For i% = 1 To 1 Step 1 

  BuildingsCount = BuildingsCount + 1
  Id% = BuildingsCount

  BWidth# = Rand(6,12)
  BHeight# = 3
  BDepth# = Rand(6,12)

  LevelsCount% = 6;Rand(1,10)

  ;some code was here...

  PositionEntity(OLight,0,(Rand(0,LevelsCount-1)*3)+1.5,0,True) ;this  provokes an error
  ;PositionEntity(OLight,0,0,0,True) ;this also provokes an error...

 ;Next

End Function