CRM 4.0 - Picklist jerarquicos

On Load(){

 var nivel;

 nivel = window.document.all.new_subcategory.DataValue

 window.document.all.new_subcategory.DeleteOption(1);
 window.document.all.new_subcategory.DeleteOption(2);
 window.document.all.new_subcategory.DeleteOption(3);
 window.document.all.new_subcategory.DeleteOption(4);
 window.document.all.new_subcategory.DeleteOption(5);
 window.document.all.new_subcategory.DeleteOption(6);
 window.document.all.new_subcategory.DeleteOption(7);
 window.document.all.new_subcategory.DeleteOption(8);
 window.document.all.new_subcategory.DeleteOption(9);

  if (window.document.all.new_category.DataValue==1){
     window.document.all.new_subcategory.AddOption("1",1);
     window.document.all.new_subcategory.AddOption("2",2);
     window.document.all.new_subcategory.AddOption("3",3);
 }
   
  if (window.document.all.new_category.DataValue==2){
     window.document.all.new_subcategory.AddOption("4",4);
     window.document.all.new_subcategory.AddOption("5",5);
     window.document.all.new_subcategory.AddOption("6",6);
 }
  if (window.document.all.new_category.DataValue==3){
     window.document.all.new_subcategory.AddOption("7",7);
     window.document.all.new_subcategory.AddOption("8",8);
     window.document.all.new_subcategory.AddOption("9",9);
 }
 window.document.all.new_subcategory.DataValue = nivel;

}


onchange(){

 var i;

 window.document.all.new_subcategory.DeleteOption(1);
 window.document.all.new_subcategory.DeleteOption(2);
 window.document.all.new_subcategory.DeleteOption(3);
 window.document.all.new_subcategory.DeleteOption(4);
 window.document.all.new_subcategory.DeleteOption(5);
 window.document.all.new_subcategory.DeleteOption(6);
 window.document.all.new_subcategory.DeleteOption(7);
 window.document.all.new_subcategory.DeleteOption(8);
 window.document.all.new_subcategory.DeleteOption(9);
 if (window.document.all.new_category.DataValue==1){
     window.document.all.new_subcategory.AddOption("1",1);
     window.document.all.new_subcategory.AddOption("2",2);
     window.document.all.new_subcategory.AddOption("3",3);
 }
   
  if (window.document.all.new_category.DataValue==2){
     window.document.all.new_subcategory.AddOption("4",4);
     window.document.all.new_subcategory.AddOption("5",5);
     window.document.all.new_subcategory.AddOption("6",6);
 }
  if (window.document.all.new_category.DataValue==3){
     window.document.all.new_subcategory.AddOption("7",7);
     window.document.all.new_subcategory.AddOption("8",8);
     window.document.all.new_subcategory.AddOption("9",9);
 }

}