Okay... I've looked through this and tried to run it to no avail. Perhaps this is because I do not have Generator. But this does not throw me out of the assisting department, oh no!
From what I can tell you have the list box populate with data based on the text file. I've done something like this before. Since I didn't have spiffy Generator, I had a "listbox" MC that contained a single "item" MC which consisted of text and a button.
When the listbox was populated with data, it would duplicate that MC for each entry, slapping the name of a user from the data into the text. The button itself would send the text back to the controlling listbox's "selected" variable.
If I wanted to do something like track what number that button was, I'd simply lean back on the naming conventions I gave to the duped MC's: the original being "item" and each subsequent MC was that name incremented (item1, item2). So to get the number of the MC I'd simply take the characters after the word "item" on the MC _name.
Umm... I realize that's a bunch of babble. Did that help any?
* Look up some tutorials on using variables, paths, and targets to pass around data