Applescript For I-Tunes Sound Clips (MAC)

i am looking for an Applescript for my Mac running OX 10.4, that will go through a highlighted playlist in I-tunes (7.6.2) and enter a start time and end time of every track. There are already several free scripts out there where the user enters the start time and the duration they want the sound clips and the script will reset all the times of the tracks in your playlist so when you make an MP3s of that tracks, you will be left with a batch sound clips. For me, the problem with these Applescripts is that not all my songs are 3 or 4 minutes long, some are 10 minutes long and they shouldn't start at one minute, they should start further in... each song is a different length. If a song is ten minutes long, there is no need to start at one minute, it wouldn't be an accurate sound clip, it should start at maybe 3 minutes in to get to the "meat" of the song. the Applescript i need should automatically set the start time at 25% into the song. The end time would work on an if/then format... If a song is only 1:30-3 minutes long, then only a 30 second sound clip, 3-5 minutes long a 45 second clip and anything above 5 minute a one minute clip. Anything below 1:30 minutes should only have maybe a 15 second clip, and below 30 seconds, no clip at all is made. Doing this on a percentage would mean on a 4 minute song, the track would then start at 1 minute and end at 1:45 minutes... and on a 10 minute song, the start time would set to 2:30 and end at 3:30. there also needs to be an un-do or a REMOVE so it would go back and uncheck the start time and end time boxes so it play at the regular start time of 0:00 to whatever the end time was... once you uncheck those boxes on i-tunes, it automatically goes back to the default times. I hope this makes sense to someone... i kind of need this on a rush.... and if i knew more about to Applescript, i could probably handle this myself. Please let me know!