Get the length of a sound, or know when it's stopped?

Can a script know the length (in secs) of a sound in the script's object's inventory? According to the wiki, llGetInventoryData only works for landmarks. I ask because I can't see any way of knowing when a sound has stopped, so knowing it's length would be the next best case. Am I missing something?

Adam

The only way I know of is manually telling the script the length, either by encoding it into the sound name or some other similarly clunky method..