Ive been using my Wacom wide tablet fine with my mac, but now I have multiple monitors.

Due to this it has mapped them both as one big screen, and due to the mapping I cant draw properly as the rations are not correct. What I want to be able to do is map the tablet so that it only functions on one screen. I have scoured the help files and cannot find a way to do this in OSX.

I have a feeling I may need some third party software, but im not sure. Can anyone help?