Short answer, no.
Long answer, Parallels is a virtual machine, emulating a certain set of hardware. It has a virtual hard drive from which it boots the OS you have installed. This virtual hard drive is a file with the extension .hdd and there is no way to make your Boot Camp windows partition look like a .hdd file.
When you have it installed, you should be able to map partitions, including the Boot Camp partition, but you still need two separate Windows installs. I'm not sure of the legality of using the same license key on each. I would have said no, but one of the editors on MacWorld apparently got the same license working after phoning Microsoft and telling the customer rep that the second install was in a virtual machine.