Want to generate automatic number for identifier data type defined in the sub node

Hi,

I want to generate an automatic number for identifier data type defined in the sub node.

Can anyone help me how i can access/retrieve the sub node elements

Here is my BO structure,

import ap.common.gdt. as apcommongdt;

businessobject  businessobject1

{

  element ID :ID
  ;

  node item [0,n]

  {

   element Item_ID :ID;

  }

}

I have already written a script for event on before save for root node in oder to generate the automatic number.

import ABSL;

var coll : collectionof ( businessobject1 )

if(this.id.IsIntial())

{

var qry  = businessobject1.querybyelements.Exceute();

if (qry.count() == 0)

{

var Newgen = 1

this.ID = Newgen.ToString();

}

else

{

coll = qry.OrderByDescending(n => n.ID);

var num = coll.GetFirst().ID;

var temp =Numeric.ParseFromstring(num);

var num1 = temp +1;

this.ID = num1.ToString();

}

}

How do i can generate a the number or write a script on sub node to acheive the same as i did for the root elements.

Thanks in advance.

Regards,

Poornima