Attach extra data to movieClip?

Hi,

Is it possible to attach some extra value/variable to movieclip?
for example, my_mc._somedata = “1”; // it would be integers between 0-xxxx

What I’m trying to do with that:
When you click movieclip, it sets selectedIndex in a list component.
(That list index_number would be “saved” on the movieclip, so I dont need search ‘for…next’ the whole list everytime movieClip is clicked…)

*edit: Ok works now, I dont need to add extra values, I just set ‘onClick’ to select the correct index for every movieclip.