CONSTANT integer WM_MOUSEWHEEL =  522  

IF message.number = WM_MOUSEWHEEL THEN 
  if i_lparam =  0  then i_lparam = lparam
  i_Perspective = integer(this.Object.gr_1.Perspective)
  
  i_Perspective = i_Perspective + ( i_lparam - lparam)/ 3000000 
  
  if i_Perspective <  1  then i_Perspective =  1 
  if i_Perspective >  100  then i_Perspective =  100 
  
  i_lparam = lparam
  this.Object.gr_1.Perspective = i_Perspective 
  
  RETURN  1  
END IF