its a one way street with the marry thing. it would be easier and less headaches just to add you 23 songs to your friends laptop.
i think there is some utility on the net that might do it like in your sceanario.
however, when i was testing it back in the day, it messed things up and you lose everything and you have to re-sync with itunes.*
i <3 apple 
- actually it just formats it, the files are still there :snky: