How to transfer music from my iPhone to iTunes?

Okay basically. I'm on holiday with my mum's laptop and i want to add more music onto my iPhone. But because it's a different iTunes my current music isn't there so i can't syn anything or else ill lose it all. Any ideas how i can get new ones on without deleting my current ones? Any help would be appreciated.

Sometimes you've just gotta sit down and think about a pringis. Then you will know the answer.

1.
Download and install onto your computer an application that will allow you to rip the files from your iPhone from
http://www.xilisoft.com/iphone-transfer.html
2

Connect your iPhone to your computer by inserting the iPhone USB cable into the device's dock connection and an open USB port on your computer.
3

Launch the iPhone ripping software on your computer. The software will guide you through the remainder of the process to transfer the files currently on the iPhone directly to iTunes (it's often as simple as clicking a single button)

source
http://iphonage.com