Is it possible to redirect the music playing on my computer through-out the line out of my iphone dock while dock is conected via USB to my computer?

It seems to me like it should be a really simple hack/mod, right?
Anyone with any ideas i'll appreciate!
Thanks

Andrew.

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iPhone 1.1.3 Fully Unlocked by master Ziphone + Geohotz
Macbook 08, 4gbRAM