iPhone Macbook & iMac Sync Issues

Hello, have a MacBook Pro, iMac and an iPhone. I can sync my music from my iMac to my iPhone, but then when I try to get it to my Macbook the sync program says it will overwrite what's on my iPhone with what's on my Macbook.

Why can I not sync my desktop and laptop with my iPhone? I can sync my contacts and calendar, but music does not work.

You can only sync your iPhone to one itunes library at a time. It sucks i know

Thanks for the reply. Any idea if this will be an upgrade in the future? My guess is it is for security reasons, but it penalizes people who actually buy two apple computers.

I have two apple computers and use one itunes library via a network disc. It takes a little tweaking with copying things to the network disc and then updating libraries but it works well.