Changing text navigation buttons in OSX
You can create custom key bindings that will apply in most OS X text editors (specifically, those that use the Cocoa framework).

Check out KeyBindingsEditor, which provides a front end to the key bindings system.

Alternatively, you can create a DefaultKeyBinding.dict plist file in ~/Library/KeyBindings/ that allows you to specify custom keybinding actions. You should read Apple's documentation for the precise actions available.

In your case, you'll probably want the moveWordForward: and moveWordBackward: methods, if I'm parsing your question correctly.