Wow, I was busy trying to translate my answer into Word for Windows when I decided to check which version you were using again. I even still have a copy of Office 2008 installed in addition to 2011.

Under Preferences, choose Spelling and Grammar. Clear the check box for "Check spelling as you type". the very first one.

Unfortunately, it won't be specific to any particular font. You will have to remember to turn it back on when you want it again.