Broke my wrist help!!

Firstly, tell your school - there's probably not a lot they can do since it will probably heal enough for the exam itself (otherwise you will have to dictate), but they could inform the exam board anyway, and they might be able to offer you a laptop or something in the meantime.

Secondly, tell your prospective universities, if applicable, as if you don't meet your offers they may make some allowances.

In terms of revision, that's difficult, but are any of the following viable?
- Typing left handed (I know you probably don't want to type, but most people can type better than write with the wrong hand).
- Dictating. Would require a willing volunteer, and they certainly wouldn't be available for all the time you need to revise, but it could help a bit.
- Non-writing learning techniques, such as testing yourself from vocab lists / formula sheets / past paper questions / textbooks. Not ideal, but still effective.
- Drawing. How bad is your left hand co-ordination? Some people can draw basic pictures, even if they can't write.
- Using a dictaphone to make notes, then playing them back to yourself.
- Voice recognition software, if you have it.

What kinds of subjects are you doing? If they are essay based, that's a real pain, but if it's maths you can actually do a lot of practice problem solving in your head, and it's really good for your memory.

Aww that sucks probably the best way is going to be using the computer! or reading text books! Failing that, group together with some friends and revise as a group so you can discuss ideas and "talk work" rather than writing, and you can voice record with your phone or something :P

Good luck with your exams!