No, you can't.
You'll have to copy all your games to another HD, and then you can make mess with the old one. WBFS is a format which won't/can't be detected by all partition programms, so your whole WBFS-Parition will be deleted anyways. Because of that, while you're at it, I suggest to screw WBFS and use FAT32 or NTFS for loading Wii-Games, much better and easier.