I just purchased a WD My Book 1TB External HDD and i have it connected to my iMac through the USB cable. Im using it to backup my iMac onto with time machine but i was wondering if there is a way i can share it with my MacBook without having to unplug it from my iMac and plug it into my MacBook? I want to beable to use Time Machine on my MacBook to backup onto the external HDD thats connect to my iMac. Is this possible?