I haven't used Notepad++ in a long time, but can't you "collapse" the functions in the editor and use CTRL+UP/DOWN (or whatever moves whole lines) to move them, along with their blocks? This way you might be able to get them into a sorted order by hand in an hour. Once that order is established, you can browse through the list and add any new function in the right spot from the beginning. I think that's what I would try.
If you insist in having a program do this after the fact, and your ActionScript functions are consistently written using the same syntax, e.g.
Code:
function some_fun()
{
code_here;
}
... then I'm sure this re-ordering could be done with a fairly simple (Python) script that someone could write for you.