extra data with listbox item

Hi,
 simple and, seems to me, should be a common question but haven't found an explanation or example of yet.

My purpose is to have some data associated with a listbox item (id, pointer, whatever). You know, from windows API the one can remember that you can set some void* with listbox or something ... that's a different approach with Symbian here, I somewhat know.

What I've done to get this is that I've implemented my own class from MListBoxModel and MTextListBoxModel (because I want a "standard" text displayed still). Implemented necessary functions.

I'm bit in trouble with correctly associating my model with listbox. I've derived yet another my own class for listbox - from CAknDoubleStyleListBox class because I found no other method of setting my own model into.
---
void CMyListBox::ConstructL( CCoeControl* aParent )
{
   iModel = (MTextListBoxModel*)new (ELeave) CMyListBoxModel;

   iListItemDrawer = new (ELeave) CTextListItemDrawer( (CTextListBoxModel*)iModel, NULL );
   CleanupStack::PushL(iListItemDrawer);
   CEikListBox::ConstructL( iModel, iListItemDrawer, aParent );
   CleanupStack::Pop(); // drawer
}
---

What I do not understand exaclty what the CEikListBox::ConstructL does. Because I see with debugger like it creates it's own iModel and iListItemDrawer anyway ... what's the point of those arguments then? And when I call listbox->Model() and cast it to my class (as I expect to be it mine), it crasehes. And not worth to mention that noone calls my inherited NumberOfItems() and ItemText.

Where am I wrong? Is it a correct approach of implementing such a small thing as wanting to have my own data associated with a single listbox item?

if you read up to this - thanks

rgds,
 Ahti.