EDIT: According to this information you can't
* Players will be unable to block attacks if they are wielding a weapon in one hand and a spell in the other. Only players who wield two handed weapons or a sword and shield can perform blocks.
http://leakerz.net/w...-facts-landing/
- You cannot block if you have a sword in one hand, and a spell in another. Only players wielding two-handed blades or sword and shield can use block.
http://gamingeverything.com/?p=1500