NSLevelIndicator (a quick "how to"):

It took all night (well its 4:18, but I’m counting it as all night) to figure this out.

Give it a name in InterfaceBuilder (click the required “on clicked” handler). There is some “call method” way of disabling clicking on it, but I don’t need to do that. Set up your ticks and values (I used 100). Name it (here it’s “LevelIndicator”).

I used this after a on drop/on open handler when my program added files:

on add_some_files(names)
	set file_count to the count of names
	set file_ratio to (100 / file_count) as integer
	set the_level to 0
          repeat with a_file from 1 to file_count
			[boring file stuff...]
		set the_level to the_level + file_ratio
		call method "setIntValue:" of (control "LevelIndicator" of window "main") with parameters {the_level}
end repeat
end  add_some_files

Ahhhh, Calgon, take me away…