For those of you with the "Excel" spreadsheet program you can look in my locker for a simple spreadsheet that determines how much of the transmission fluid is changed out with subsequent drain & refills - I admit I stole this from somewhere on the net (but don't remember), so no credit to me is do if you like it.
EZ link to my locker....
http://www.subaru-svx.net/photos/user.php?lee