listBox (sample C#)

In Visual Cobol i try:

- Create a listBox1

- Add Itens:

     invoke listBox1::"Items"::"Add"("Item 1")
            invoke listBox1::"Items"::"Add"("Item 2")

- But now, can i get INDEX from doubleClick event?

i try: invoke type MessageBox::Show(listBox1::Text), but, show only TEXT. But a need INDEX (0,1,2,3...)