List box control

Question

hi

i  added a collection of data into a list box. i have another group of data with a group name.i want to add this group in to that same list box as a tree structure. 

the sample list box is shown below.

item1

item 2

item3

-group name

  group item1

  group item 2

  group item 3

item 4

item 5

is there any way to do this. when clicking on the group name it must be expanded within the list box and i want to manage all these elements with an index.

Thanx in advance .