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My Mac has OS X installed on one partition and Windows 8 installed in another partition. However, OS X comes with a utility called Boot Camp Assistant that facilitates this process, so I don't know how that'd work with Ubuntu / Windows 8 / Windows 7.
If you have enough space for another partition on your hard drive, there's no reason it shouldn't be possible. Windows 8 will probably trash GRUB if you use it as your boot loader though, so you might have to reinstall it afterwards. If you use the Windows bootloader it'll probably be fine.